I haven't revisited this since my original post, back then I just found another bass realtrack that worked for the song I was working on and moved on.

I just tested again this morning and it is working fine for me, I tried my original song which was in Em and had the problem where the bass would randomly switch to the "IV" chord, and it worked fine; it stayed on the "I" unless told otherwise.

I then transposed the song to Cm and it also worked.

Note: I'm still using BIAB 2019, my BIAB 2020 has not arrived yet, so not exactly the same as you.

The date of my RBass182.ST2 file is 2019-03-13