for my own Ableton support request we went back and forth and the problem slowly resolved itself after a few things
A complete fresh install didn't work, but using the newest version of Max 8 and then telling Live to use that version ... that eventually seemed to work. It was unusual though, as the crashes slowly abated. As if there was corruption in the database, or paths, which were slowly getting updated.
I have a couple of sets which still can tend to crash on loading them, perhaps 1 in 5 times. But I've spent so long chasing bugs I had to abandon bug hunting at that point and dedicate some time to other things.
Regarding the BCRXL script I've yet to follow up on that and I think it's a separate issue.