Notes keep on playing

Musescore 3.5.0.13199. I've had this problem occasionally over the last few months. The notes on one instrument line in a multi-instrument score keep on playing, each note overlaying the ones to come until it all reaches a horrible disconsonant crescendo.

I can change the instrument to which this happens by rearranging the order of instruments in "Instruments". It seems to only happen to the second instrument in the score (even if the first instrument contains one or several staves). In the past I was able make it go away by restarting the program. Now I have a score where that doesn't work. Open and close the score, restart the program, it's still a problem. Also tried restarting the audio devices, disabling the synth and no fix.

I can mute the problematic instrument line (ie the second instrument) and what is now the second instrument does the same 'note-sustaining' problem.

(Later). OK, I thought I'd better restart the computer and now it's gone. It's a little irritating though. Has anyone had this problem. Any ideas why it happens, or more importantly how I might fix it without restarting my machine?