I'm using Ubuntu Mate 22.04. Sometimes, usually when I'm already doing something resource-intensive, such as converting a video, and then I try to do something else that's also resource-intensive, suddenly, the two panels that I have (top and bottom) become invisible and I can't get them back in any way. They don disappear, that is, I can still click on elements of them and get them to work that way; they just become invisible, that is, instead of the panels, I just see the topmost and bottommost parts of my wallpaper.
The bug disappears when I reboot, but I don't like to do that in the middle of, for instance, converting a video. Also, the usual shutdown or reboot menu doesn't work in that state; in order to reboot then, I have to open a terminal and type reboot.
Since this usually happens when I'm trying to do two resource-intensive things at the same time, I could, of course, simply not do two resource-intensive things at the same time. But that kind of reminds me of the old groaner of a joke where someone goes to the doctor and says "It hurts really badly when I press here", and the doctor says "Then I wouldn't press there".
I've once managed it to take a screenshot when that bug appeared. Blacked-out areas were blacked out for privacy reasons:
