Follow up in case anyone is following the thread.

I've been working with BIAB almost daily since I started the thread. I've had no crashes at all since I posted the last one on March 26. Solved, I hope, although I never determined the cause.
Equipment: Yamaha 5'6" grand piano. BIAB for Macintosh 2017 --> 2020. MacBook Pro. Focusrite 2i2, Yamaha YC 88 keyboard

"Why do I have to go to school, Grandad? If I watch YouTube I'll know everything!"
- Grandson #3