Basically the error come from g70 and I try to explain what I understood:

XG Midi files should not be mixed with Make Up Tools sysexc
this is why BK doesn't allow you to enter MKT with this XG files
G70 doesn't have such control, so you can enter MKT and add MKT sysexc into XG MIDI files.
On BK, these hybrid MIDI files doesn't work correctly that's why you are listening piano instead of Drum

This is what I understood from a technician's explanation...
some kind of fixing should come indeed...
hope it helps...

best regards