I have had issues with BIAB not playing slash chords properly. Happens to me if I hold or rest a slash chord for the first two beats of a four beat bar, then have a straight (no slash bass, no holds or rest) chord for the third beat, the bass will play the bass note indicated in the previous slash chord. I can get around it be changing the bar to 2 - two beat bars. Easy enough to do but still a minor annoyance. Don't know if you have a similar layout in the songs giving you trouble - might be something to look at.
Good luck.