I can't reproduce the issue at will. However Musescore is more apt to crash on me in Version 4. Sometimes if i click on a note marking or am moving chords around with the arrow keys or selecting something on the score it will abruptly crash. Additionally, if I'm working with multiple windows and 1 of those windows crash, I can't get the score I was working on back. The "musecore crashed suddenly do you want to recover your work" won't work for that lost instance. Even if I use task manager to kill all of my musescore instances I still can't get it back. This is upsetting. Musescore 3 never crashed on me.
Another suggestion though is the piano keys are not highlighting the correct keys when the 8v a/b is used.