Q: TF26212 Error is coming while saving work item in TFS 2010 I have created a workitem type named 'Bug_Tracker', with states & Transtitions well defined. 
When a new bug is created using this workitem, it gets assigned to developer, but when developer marks it as 'Resolved' and assign back to QA, following error comes on saving workitem:-
"TF26212: Team Foundation Server could not save your changes. There may be problems with the work item type definition. Try again or contact your Team Foundation Server administrator."
Following is the XML for the workitem - 
<q1:WITD application="Work item type editor" version="1.0" xmlns:q1="http://schemas.microsoft.com/VisualStudio/2008/workitemtracking/typedef">
  <WORKITEMTYPE name="Bug Tracker">
    DESCRIPTION>Describes a divergence between required and actual behavior, and tracks the work done to correct the defect and verify the correction.</DESCRIPTION>
    <FIELDS>
      FIELD reportable="dimension" refname="System.Title" name="Title" type="String">
        <REQUIRED />
        <HELPTEXT>Stories affected and how</HELPTEXT>
      </FIELD>
      <FIELD reportable="dimension" refname="System.State" name="State" type="String">
        <HELPTEXT>Change on reviewing, fixing or verifying the fix. Active = not yet fixed; Resolved = fix not yet verified; Closed = fix verified.</HELPTEXT>
      </FIELD>
      FIELD reportable="dimension" refname="System.Rev" name="Rev" type="Integer" />
      <FIELD reportable="dimension" refname="System.ChangedBy" name="Changed By" syncnamechanges="true" type="String">
        <ALLOWEXISTINGVALUE />
        <VALIDUSER />
      </FIELD>
      <FIELD refname="Microsoft.VSTS.TCM.SystemInfo" name="System Info" type="HTML">
        <HELPTEXT>Test context, provided automatically by test infrastructure</HELPTEXT>
      </FIELD>
      FIELD refname="Microsoft.VSTS.TCM.ReproSteps" name="Repro Steps" type="HTML">
        <HELPTEXT>How to see the bug. End by contrasting expected with actual behavior.</HELPTEXT>
      </FIELD>
      <FIELD refname="Microsoft.VSTS.Common.StateChangeDate" name="State Change Date" type="DateTime">
        <WHENCHANGED field="System.State">
          <SERVERDEFAULT from="clock" />
        </WHENCHANGED>
        <WHENNOTCHANGED field="System.State">
          <READONLY />
        </WHENNOTCHANGED>
      /FIELD>
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.ActivatedDate" name="Activated Date" type="DateTime">
        <WHENNOTCHANGED field="System.State">
          <READONLY />
        </WHENNOTCHANGED>
      /FIELD>
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.ActivatedBy" name="Activated By" syncnamechanges="true" type="String">
        <WHENNOTCHANGED field="System.State">
          <ALLOWEXISTINGVALUE />
          <READONLY />
        </WHENNOTCHANGED>
      </FIELD>
      <FIELD reportable="dimension" refname="System.Reason" name="Reason" type="String">
        <HELPTEXT>The reason why the bug is in the current state</HELPTEXT>
      </FIELD>
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.ResolvedBy" name="Resolved By" syncnamechanges="true" type="String">
        <WHENNOTCHANGED field="System.State">
          <ALLOWEXISTINGVALUE />
          <READONLY />
        </WHENNOTCHANGED>
      </FIELD>
      <FIELD reportable="dimension" refname="System.AssignedTo" name="Assigned To" syncnamechanges="true" type="String">
        <ALLOWEXISTINGVALUE />
        <VALIDUSER />
        <HELPTEXT>The person currently working on this bug</HELPTEXT>
      </FIELD>
      <FIELD reportable="dimension" refname="System.WorkItemType" name="Work Item Type" type="String" />
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.ClosedBy" name="Closed By" syncnamechanges="true" type="String">
        <WHENNOTCHANGED field="System.State">
          <ALLOWEXISTINGVALUE />
          <READONLY />
        </WHENNOTCHANGED>
      </FIELD>
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.Priority" name="Priority" type="Integer">
        <ALLOWEDVALUES>
          <LISTITEM value="1" />
          <LISTITEM value="2" />
          <LISTITEM value="3" />
          <LISTITEM value="4" />
        </ALLOWEDVALUES>
        <DEFAULT from="value" value="2" />
        <HELPTEXT>Business importance. 1=must fix; 4=unimportant.</HELPTEXT>
      </FIELD>
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.ResolvedReason" name="Resolved Reason" type="String">
        <ALLOWEDVALUES>
          <LISTITEM value="As Designed" />
          <LISTITEM value="Cannot Reproduce" />
          <LISTITEM value="Deferred" />
          <LISTITEM value="Duplicate" />
          <LISTITEM value="Fixed" />
          <LISTITEM value="Obsolete" />
        </ALLOWEDVALUES>
        <FROZEN />
        <HELPTEXT>The reason why the bug was resolved</HELPTEXT>
      </FIELD>
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.StackRank" name="Stack Rank" type="Double">
        <HELPTEXT>Work first on items with lower-valued stack rank. Set in triage.</HELPTEXT>
      </FIELD>
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Build.IntegrationBuild" name="Integration Build" type="String">
        <SUGGESTEDVALUES>
          <LISTITEM value="&lt;None&gt;" />
        </SUGGESTEDVALUES>
        <SUGGESTEDVALUES filteritems="excludegroups">
          <GLOBALLIST name="Builds - TranstutorsProjects" />
        </SUGGESTEDVALUES>
        <HELPTEXT>The build in which the bug was fixed</HELPTEXT>
      </FIELD>
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Build.FoundIn" name="Found In" type="String">
        <SUGGESTEDVALUES>
          <LISTITEM value="&lt;None&gt;" />
        </SUGGESTEDVALUES>
        <SUGGESTEDVALUES filteritems="excludegroups">
          <GLOBALLIST name="Builds - TranstutorsProjects" />
        </SUGGESTEDVALUES>
        <HELPTEXT>The build in which the bug was found</HELPTEXT>
      </FIELD>
      <FIELD reportable="dimension" refname="System.CreatedDate" name="Created Date" type="DateTime" />
      <FIELD reportable="dimension" refname="System.CreatedBy" name="Created By" syncnamechanges="true" type="String" />
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.Severity" name="Severity" type="String">
        <ALLOWEDVALUES>
          <LISTITEM value="1 - Critical" />
          <LISTITEM value="2 - High" />
          <LISTITEM value="3 - Medium" />
          <LISTITEM value="4 - Low" />
        </ALLOWEDVALUES>
        <DEFAULT from="value" value="3 - Medium" />
        <HELPTEXT>Assessment of the effect of the bug on the project</HELPTEXT>
      </FIELD>
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.ResolvedDate" name="Resolved Date" type="DateTime">
        <WHENNOTCHANGED field="System.State">
          <READONLY />
        </WHENNOTCHANGED>
      </FIELD>
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.ClosedDate" name="Closed Date" type="DateTime">
        <WHENNOTCHANGED field="System.State">
          <READONLY />
        </WHENNOTCHANGED>
      </FIELD>
      <FIELD refname="System.Description" name="Description" type="PlainText" />
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.ReopenedDate" name="Reopened Date" type="DateTime">
        <WHENNOTCHANGED field="System.State">
          <READONLY />
        </WHENNOTCHANGED>
      </FIELD>
      <FIELD refname="System.History" name="History" type="History">
        <HELPTEXT>Discussion thread plus automatic record of changes</HELPTEXT>
      </FIELD>
      <FIELD reportable="dimension" refname="Microsoft.VSTS.Common.ReopenedBy" name="Reopened By" type="String">
        <WHENNOTCHANGED field="System.State">
          <ALLOWEXISTINGVALUE />
          <READONLY />
        </WHENNOTCHANGED>
      </FIELD>
      <FIELD refname="System.RelatedLinkCount" name="Related Link Count" type="Integer" />
      <FIELD reportable="dimension" refname="System.IterationPath" name="Iteration Path" type="TreePath">
        <HELPTEXT>The iteration within which this bug will be fixed</HELPTEXT>
      </FIELD>
      <FIELD refname="System.IterationId" name="Iteration ID" type="Integer" />
      <FIELD refname="System.ExternalLinkCount" name="External Link Count" type="Integer" />
      <FIELD reportable="dimension" refname="System.TeamProject" name="Team Project" type="String" />
      <FIELD refname="System.HyperLinkCount" name="Hyperlink Count" type="Integer" />
      <FIELD refname="System.AttachedFileCount" name="Attached File Count" type="Integer" />
      <FIELD refname="System.NodeName" name="Node Name" type="String" />
      <FIELD reportable="dimension" refname="System.AreaPath" name="Area Path" type="TreePath">
        <HELPTEXT>The area of the product with which this bug is associated</HELPTEXT>
      </FIELD>
      <FIELD reportable="detail" refname="System.RevisedDate" name="Revised Date" type="DateTime" />
      <FIELD reportable="dimension" refname="System.ChangedDate" name="Changed Date" type="DateTime" />
      <FIELD reportable="dimension" refname="System.Id" name="ID" type="Integer" />
      <FIELD refname="System.AreaId" name="Area ID" type="Integer" />
      <FIELD refname="System.AuthorizedAs" name="Authorized As" syncnamechanges="true" type="String" />
    </FIELDS>
    <WORKFLOW>
      <STATES>
        <STATE value="Resolved">
          <FIELDS>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedReason">
              <REQUIRED />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedDate">
              <EMPTY />
            </FIELD>
          </FIELDS>
        </STATE>
        <STATE value="Closed">
          <FIELDS>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedReason">
              <READONLY />
            </FIELD>
          </FIELDS>
        </STATE>
        <STATE value="Verified">
          <FIELDS>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedDate">
              <SERVERDEFAULT from="clock" />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedReason">
              <REQUIRED />
            </FIELD>
          </FIELDS>
        </STATE>
        <STATE value="New">
          <FIELDS>
            <FIELD refname="Microsoft.VSTS.Common.ActivatedDate">
              <SERVERDEFAULT from="clock" />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ActivatedBy">
              <COPY from="currentuser" />
              <REQUIRED />
              <VALIDUSER />
            </FIELD>
            <FIELD refname="System.AssignedTo">
              <DEFAULT from="currentuser" />
            </FIELD>
          </FIELDS>
        </STATE>
      </STATES>
      <TRANSITIONS>
        <TRANSITION from="" to="New">
          <REASONS>
            <DEFAULTREASON value="New Bug" />
          </REASONS>
          <FIELDS>
            <FIELD refname="Microsoft.VSTS.Common.ActivatedBy">
              <ALLOWEXISTINGVALUE />
              <COPY from="currentuser" />
              <VALIDUSER />
              <REQUIRED />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ActivatedDate">
              <SERVERDEFAULT from="clock" />
            </FIELD>
            <FIELD refname="System.AssignedTo">
              <COPY from="field" field="System.CreatedBy" />
            </FIELD>
          </FIELDS>
        </TRANSITION>
        <TRANSITION from="New" to="Resolved">
          <ACTIONS>
            <ACTION value="Microsoft.VSTS.Actions.Checkin" />
          </ACTIONS>
          <REASONS>
            <REASON value="Deferred">
              <FIELDS>
                <FIELD refname="Microsoft.VSTS.Common.ResolvedReason">
                  <COPY from="value" value="Deferred" />
                  <ALLOWEDVALUES>
                    <LISTITEM value="Deferred" />
                  </ALLOWEDVALUES>
                </FIELD>
              </FIELDS>
            </REASON>
            <REASON value="Duplicate">
              <FIELDS>
                <FIELD refname="Microsoft.VSTS.Common.ResolvedReason">
                  <COPY from="value" value="Duplicate" />
                  <ALLOWEDVALUES>
                    <LISTITEM value="Duplicate" />
                  </ALLOWEDVALUES>
                </FIELD>
              </FIELDS>
            </REASON>
            <REASON value="As Designed">
              <FIELDS>
                <FIELD refname="Microsoft.VSTS.Common.ResolvedReason">
                  <COPY from="value" value="As Designed" />
                  <ALLOWEDVALUES>
                    <LISTITEM value="As Designed" />
                  </ALLOWEDVALUES>
                </FIELD>
              </FIELDS>
            </REASON>
            <REASON value="Cannot Reproduce">
              <FIELDS>
                <FIELD refname="Microsoft.VSTS.Common.ResolvedReason">
                  <COPY from="value" value="Cannot Reproduce" />
                  <ALLOWEDVALUES>
                    <LISTITEM value="Cannot Reproduce" />
                  </ALLOWEDVALUES>
                </FIELD>
              </FIELDS>
            </REASON>
            <REASON value="Obsolete">
              <FIELDS>
                <FIELD refname="Microsoft.VSTS.Common.ResolvedReason">
                  <COPY from="value" value="Obsolete" />
                  <ALLOWEDVALUES>
                    <LISTITEM value="Obsolete" />
                  </ALLOWEDVALUES>
                </FIELD>
              </FIELDS>
            </REASON>
            <DEFAULTREASON value="Fixed">
              <FIELDS>
                <FIELD refname="Microsoft.VSTS.Common.ResolvedReason">
                  <COPY from="value" value="Fixed" />
                  <ALLOWEDVALUES>
                    <LISTITEM value="Fixed" />
                  </ALLOWEDVALUES>
                </FIELD>
              </FIELDS>
            </DEFAULTREASON>
          </REASONS>
          <FIELDS>
            <FIELD refname="System.AssignedTo">
              <COPY from="field" field="System.CreatedBy" />
              <ALLOWEXISTINGVALUE />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ActivatedDate">
              <READONLY />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ActivatedBy">
              <ALLOWEXISTINGVALUE />
              <READONLY />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedBy">
              <ALLOWEXISTINGVALUE />
              <COPY from="currentuser" />
              <VALIDUSER />
              <REQUIRED />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedDate">
              <SERVERDEFAULT from="clock" />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedReason">
              <COPY from="value" value="Fixed" />
            </FIELD>
          </FIELDS>
        </TRANSITION>
        <TRANSITION from="Resolved" to="Verified">
          <REASONS>
            <DEFAULTREASON value="Fixed" />
          </REASONS>
          <FIELDS>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedBy">
              <ALLOWEXISTINGVALUE />
              <COPY from="currentuser" />
              <VALIDUSER />
              <REQUIRED />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedDate">
              <SERVERDEFAULT from="clock" />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedReason">
              <COPY from="value" value="Fixed" />
            </FIELD>
          </FIELDS>
        </TRANSITION>
        <TRANSITION from="Verified" to="Resolved">
          <REASONS>
            <REASON value="Reopened" />
            <DEFAULTREASON value="Not fixed" />
          </REASONS>
          <FIELDS>
            <FIELD refname="Microsoft.VSTS.Common.ActivatedBy">
              <ALLOWEXISTINGVALUE />
              <COPY from="currentuser" />
              <VALIDUSER />
              <REQUIRED />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ActivatedDate">
              <SERVERDEFAULT from="clock" />
            </FIELD>
            <FIELD refname="System.AssignedTo">
              <COPY from="field" field="Microsoft.VSTS.Common.ResolvedBy" />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ReopenedBy">
              <ALLOWEXISTINGVALUE />
              <COPY from="currentuser" />
              <VALIDUSER />
              <REQUIRED />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ReopenedDate">
              <SERVERDEFAULT from="clock" />
            </FIELD>
          </FIELDS>
        </TRANSITION>
        <TRANSITION from="Verified" to="Closed">
          <REASONS>
            <DEFAULTREASON value="Verified Fixed" />
          </REASONS>
          <FIELDS>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedBy">
              <ALLOWEXISTINGVALUE />
              <READONLY />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ResolvedDate">
              <READONLY />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ClosedDate">
              <SERVERDEFAULT from="clock" />
            </FIELD>
            <FIELD refname="Microsoft.VSTS.Common.ClosedBy">
              <ALLOWEXISTINGVALUE />
              <COPY from="currentuser" />
              <VALIDUSER />
              <REQUIRED />
            </FIELD>
          </FIELDS>
        </TRANSITION>
      </TRANSITIONS>
    </WORKFLOW>
    <FORM>
      <Layout>
        <Group>
          <Column PercentWidth="100">
            <Control FieldName="System.Title" Type="FieldControl" Label="&amp;Title:" LabelPosition="Left" />
          </Column>
        </Group>
        <Group>
          <Column PercentWidth="50">
            <Group Label="Status">
              <Column PercentWidth="100">
                <Control FieldName="System.State" Type="FieldControl" Label="&amp;State:" LabelPosition="Left" />
                <Control FieldName="System.Reason" Type="FieldControl" Label="&amp;Reason:" LabelPosition="Left" />
                <Control FieldName="Microsoft.VSTS.Common.ResolvedReason" Type="FieldControl" Label="Resolved Reason:" LabelPosition="Left" ReadOnly="True" />
                <Control FieldName="System.AssignedTo" Type="FieldControl" Label="Assigned To:" LabelPosition="Left" />
              </Column>
            </Group>
          </Column>
          <Column PercentWidth="50">
            <Group Label="Classification">
              <Column PercentWidth="100">
                <Control FieldName="System.AreaPath" Type="WorkItemClassificationControl" Label="&amp;Area:" LabelPosition="Left" />
                <Control FieldName="System.IterationPath" Type="WorkItemClassificationControl" Label="Ite&amp;ration:" LabelPosition="Left" />
              </Column>
            </Group>
          </Column>
        </Group>
        <Group>
          <Column PercentWidth="100">
            <Group Label="Planning">
              <Column PercentWidth="33">
                <Control FieldName="Microsoft.VSTS.Common.StackRank" Type="FieldControl" Label="Stack Ran&amp;k:" LabelPosition="Left" NumberFormat="DecimalNumbers" MaxLength="10" />
              </Column>
              <Column PercentWidth="33">
                <Control FieldName="Microsoft.VSTS.Common.Priority" Type="FieldControl" Label="&amp;Priority:" LabelPosition="Left" />
              </Column>
              <Column PercentWidth="33">
                <Control FieldName="Microsoft.VSTS.Common.Severity" Type="FieldControl" Label="Se&amp;verity:" LabelPosition="Left" />
              </Column>
            </Group>
          </Column>
        </Group>
        <TabGroup>
          <Tab Label="Details">
            <Group>
              <Column PercentWidth="50">
                <Control FieldName="Microsoft.VSTS.TCM.ReproSteps" Type="HtmlFieldControl" Label="Steps to Repro&amp;duce:" LabelPosition="Top" Dock="Fill" MinimumSize="(100,200)" />
              </Column>
              <Column PercentWidth="50">
                <Control FieldName="System.History" Type="WorkItemLogControl" Label="&amp;History:" LabelPosition="Top" Dock="Fill" />
              </Column>
            </Group>
          </Tab>
          <Tab Label="System Info">
            <Group>
              <Column PercentWidth="50">
                <Control FieldName="Microsoft.VSTS.Build.FoundIn" Type="FieldControl" Label="&amp;Found in Build:" LabelPosition="Left" />
              </Column>
              <Column PercentWidth="50">
                <Control FieldName="Microsoft.VSTS.Build.IntegrationBuild" Type="FieldControl" Label="In&amp;tegrated in Build:" LabelPosition="Left" />
              </Column>
            </Group>
            <Control FieldName="Microsoft.VSTS.TCM.SystemInfo" Type="HtmlFieldControl" Label="System I&amp;nfo:" LabelPosition="Top" Dock="Fill" />
          </Tab>
          <Tab Label="Test Cases">
            <Control Type="LinksControl" Label="Test &amp;Cases testing this Bug:" LabelPosition="Top" Name="TestedBy">
              <LinksControlOptions>
                <LinkColumns>
                  <LinkColumn RefName="System.ID" />
                  <LinkColumn RefName="System.WorkItemType" />
                  <LinkColumn RefName="System.Title" />
                  <LinkColumn RefName="System.AssignedTo" />
                  <LinkColumn RefName="System.State" />
                  <LinkColumn LinkAttribute="System.Links.Comment" />
                </LinkColumns>
                <WorkItemLinkFilters FilterType="include">
                  <Filter LinkType="Microsoft.VSTS.Common.TestedBy" FilterOn="forwardname" />
                </WorkItemLinkFilters>
                <ExternalLinkFilters FilterType="excludeAll" />
                <WorkItemTypeFilters FilterType="include">
                  <Filter WorkItemType="Test Case" />
                </WorkItemTypeFilters>
              </LinksControlOptions>
            </Control>
          </Tab>
          <Tab Label="All Links">
            <Control Type="LinksControl" LabelPosition="Top" Name="GeneralLinks">
              <LinksControlOptions>
                <LinkColumns>
                  <LinkColumn RefName="System.ID" />
                  <LinkColumn RefName="System.WorkItemType" />
                  <LinkColumn RefName="System.Title" />
                  <LinkColumn RefName="System.AssignedTo" />
                  <LinkColumn RefName="System.State" />
                  <LinkColumn LinkAttribute="System.Links.Comment" />
                </LinkColumns>
                <WorkItemLinkFilters FilterType="includeAll" />
                <ExternalLinkFilters FilterType="includeAll" />
                <WorkItemTypeFilters FilterType="includeAll" />
              </LinksControlOptions>
            </Control>
          </Tab>
          <Tab Label="Attachments">
            <Control Type="AttachmentsControl" LabelPosition="Top" />
          </Tab>
        </TabGroup>
      </Layout>
    </FORM>
  </WORKITEMTYPE>
</q1:WITD>

Any help in this regard is highly appreciated !
