Deadlock when shifting notes

I was moving notes up and down the staff with the arrow keys.
Suddenly musescore froze, with the macos beachball.
I sampled the process before force quitting (attached).
The only unusual thing I can think of is that I switched audio to my bluetooth headphones part way through the session.
Hope you can track down the cause.
Some MIDI activity and QMutex is visible in the process sample.