Shane:

I see what you mean about the 7ths.
You might try this and see how it sounds. (using the SWABBIE file)
- Copy only the chords from bar 53 at the key change to the end
- Open a "new" instance of BIAB
- Set the key to B
- Paste those chords to the new grid

See if that sounds the way you want for the last part of the song.
That might help figure out where BIAB is going wrong.
(I think you can use Copy/Paste in BIAB 2020, I forget!)

LLOYD S