  We investigate the roles of disorder on low-temperature transport in SmB$_6$
crystals grown by both the Al flux and floating zone methods. We used the
inverted resistance method with Corbino geometry to investigate whether
low-temperature variations in the standard resistance plateau arises from a
surface or a bulk channel in floating zone samples. The results show
significant sample-dependent residual bulk conduction, in contrast to smaller
amounts of residual bulk conduction previously observed in Al flux grown
samples with Sm vacancies. We consider hopping in an activated impurity band as
a possible source for the observed bulk conduction, but it is unlikely that the
large residual bulk conduction seen in floating zone samples is solely due to
Sm vacancies. We therefore propose that one-dimensional defects, or
dislocations, contribute as well. Using chemical etching, we find evidence for
dislocations in both flux and floating zone samples, with higher dislocation
density in floating zone samples than in Al flux grown samples. In addition to
the possibility of transport through one-dimensional dislocations, we also
discuss our results in the context of recent theoretical models of SmB$_6$.
