i know it seems a bit strange, but do this test, link your device with your phone by Bluetooth, check voices, if you remain the same restart to drums and check voices again.
for strange that it seems, I am with a device that happens the same with the voices, but NOT installed patch.
as @Biggerdave says if MDC eliminates something, it would not be much problem, it normally eliminates if it has a map not installed by MDC, maybe something else.
regards