Firstly, I have reported this problem and referred the developers to this thread in the Windows Updates beta testing forum.
In the meantime, go to the link below and download update #263 or #266. I am not sure if Mac BIAB behaves the same as Windows BIAB but installing an earlier update in Windows takes BIAB back to that update.
I've done this a couple of times over the years when an update has not been friendly with my computer or BIAB and it has solved my existing problems (at that time).
I'm not sure if you want to try it or not. I'll leave it to you.
https://www.pgmusic.com/support_macintoshupdates.htmHopefully someone from BIAB will see my post regarding this thread soon.
What I encourage you to do is to write to support@pgmusic.com once more and refer them to this thread so that they can see all that has been tried. It will also help them isolate the problem.