MuseScore 4 Playback is insanely fast and static sounding - but works after 5 minutes

I'm using version 4.0.0 on Linux Mint 20 and previously used version 3 without issue.

When opening a saved score, and attempting to play a score, the playback time is a matter of a few fractions of a second, and the sound is a static mess. Repeated attempts to playback result in the same insane speed.

However, if I leave the score alone, go make a cup of tea and come back a few minutes (maybe 5) later, it plays fine.

If I now open a second score, this one won't playback correctly, but the first one I opened continues to do so every time. If I wait another 5 minutes, the second one now plays.

The same thing seems to happen if I create a new score from scratch. I start entering notes, and all I hear is a short static sound with each note pressed. Wait 5 minutes, and then note entry starts behaving and playback also works.

It's like there's some sort of 5-minute i/0 device timeout which happens with every score that's opened.