I had the same occurance with a solo instrument. The Bass, Drums and Guitar all were able to transfer from BIAB to RB without problem. However, a trumpet part was changed from this beautiful solo to this sterile ping-pong sounding MIDI file. You mentioned that it can depend on end user configurations. But, I hope there would be a better answer. It is a bummer when you get a nice solo, move it to RB to continue composing only to discover this dread awful MIDI tone.