Sigh. Sorry for the misdirection. It worked for me. But…
The developers and QA folks are having a tough time tracking this one down. It is not yet clear what exact set of steps, number of tracks, selectedness, etc. are needed to reliably reproduce it.
Thank you so much. Until I figured out that it was related to sync-lock, it was driving me nuts. Even now, I still accidentally crash and have to recover work. I really appreciate you and everyone chasing this down.