Chris, I still think your Roland is not set to GM mode because of your problem with the drums. Just being in Multitimbral mode is not necessarily GM mode. I downloaded the manual for your keyboard and what a mess that thing is! As far as I can tell, there's no mention anywhere of GM/GS, GM2, playing SMF's which is Standard Midi File, none of that. It's ridiculous. It's another example of how manufacturer's give GM the short shrift even though Roland specifically makes a big deal out of it being fully GM/GM2 compatible on their website. You would think there would be a simple entry in the index titled "if you want to play a SMF, do this". I did this before I had to leave for work so maybe it's there but I missed it. If you have Adobe Pro, try a keyword search in the online manual.
I have a Roland Sonic Cell and it has to be in Performanc Mode to access the GM soundbank. When I play Biab with it, it just goes there automatically. If I''m using RB to play a midi file, same thing. Try putting your keyboard in Performance mode and see what happens. Also in Biab see the menu bar at the very top of the screen. In the middle is the GM menu. Click on that and one of the entry's in that combo box is something like send GM or GS at startup. Play with those entries and see if that does it. GS is the Roland General Midi standard, try that one first but try the GM one as well. As I said earlier, playing Biab using GM should be a no brainer. 30 seconds max. If none of this works, try going to one of the Roland user forums like this one Rolandclan I feel your pain, man. I hate this crap with a manual not explaining the most basic things.

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.