I've found that on Windows 10 1703 using the key value "Encryption Method" causes the task sequence step to fail. MBAM policy creates the value as "Encryption MethodWithXtsOs" but although the step completes successfuly that the pre-provision step ignores it. Do you experience the same behaviour?
There seems to be some inconsistency in the results of using "Encryption Method" and "Encryption MethodWithXtsOs", I am deploying Windows 10 1703 in ConfigMgr 1706 with MDT Integration and saving BitLocker Recovery to AD until MBAM is implemented, the BitLocker Pre-provision step did not work with the "Encryption MethodWithXtsOs" registry option, but did when I added the "Encryption Method" registry option.
Subtle changes and reversions seem to be implemented without adequate documentation from Microsoft.
I'm not seeing this "issue" with Windows 10 1703 or/and CM1706. But thanks for your workarround!
Thanks for that, Can you post your regfiles? Do you use Windows 10 1709 or a different build?