Program has crashed four times today while playing.

I upgraded to Big Sur recently on my iMac Pro. Is that it?

Sorry to hear this. I suggest you ask in the BIAB for Mac forum, here: https://www.pgmusic.com/forums/ubbthreads.php?ubb=postlist&Board=39&page=1

You are much more likely to find others who can answer and help.

Thanks. Will do

There's a patch update required for BIAB to work properly on Big Sur. You can download it here:
https://www.pgmusic.com/support_macintoshupdates.htm#2020_423