That's a tricky one especially for someone new at this, glad you figured it out. One question though, if there was an "extra" wav file, didn't that show up on the RB track screen? I would think if you heard something like that, you would start soloing each track to isolate which one is causing the problem. If I heard something like that, I wouldn't even think about it, I would erase that track and simply generate a new one by right clicking on the track and either pick a Real Track or if you want a Biab midi style to be applied, select a style, right click the track, click midi and then pick the instrument. Problem gone. I'm somewhat aware of all these kinds of things but this is a major reason why RB is rapidly becoming my primary program now. Remember, RB has the same chord grid, you can set all the same part markers, access all the same styles and Real Tracks/Drums. Something like this is easy to fix in RB and I really don't care what I may have done in Biab to create the problem in the first place.
Something that still may get you is when you save in RB, it will save either as a .seq if there's audio tracks or a midi file. Since we're all using RT/RD's there's basically always at least one audio track in there so it will be an .seq. That won't open in Biab only RB so you now have a separate version of your song. I keep those files in a separate directory from the Biab ones.

Bob

Biab/RB latest build, Win 11 Pro, Ryzen 5 5600 G, 512 Gig SSD, 16 Gigs Ram, Steinberg UR22 MkII, Roland Sonic Cell, Kurzweil PC3, Hammond SK1, Korg PA3XPro, Garritan JABB, Hypercanvas, Sampletank 3, more.