Why not start with midi drums in BIAB? Can you export the WMA drum files to a single midi track and see if they play as you want in another program like RB and not your DAW. If they don't the problem is in BIAB. If they do the problem is in your DAW. The reason I suggest midi drums is that I imagine WMA drums must be one of the hardest audio to midi conversions. But I may be wrong!