  Even at the lowest accessible temperatures, measurements of the quantum
anomalous Hall (QAH) effect have indicated the presence of parasitic
dissipative conduction channels. There is no consensus whether parasitic
conduction is related to processes in the bulk or along the edges. Here, we
approach this problem by comparing transport measurements of Hall bar and
Corbino geometry devices fabricated from Cr-doped (BiSb)$_2$Te$_3$. We identify
bulk conduction as the dominant source of dissipation at all values of
temperature and in-plane electric field. Furthermore, we observe identical
breakdown phenomenology in both geometries, indicating that breakdown of the
QAH phase is a bulk process. The methodology developed in this study could be
used to identify dissipative conduction mechanisms in new QAH materials,
ultimately guiding material development towards realization of the QAH effect
at higher temperatures.
