[alaxapta7]

Same, although I haven't seen this one for a while now. One way to fix the misbehaving explorer (which start menu, tray and others are part of) is to simply kill it and start it over from the task manager. Some applications failed to re-create their tray icons after this, but either all of them fixed it, or it got somehow fixed in Windows.

[Tigress8780]

This still happens on my Windows 11 machines (the tooltip stays there unless you move the mouse over the same icon again), but only to a small number of applications. Makes me wonder if they are using a different set of API to set up their tray icons.