Well, I was unable to spend much time in Gnome to reproduce the effect or refute it.
OTOH it wasn't reproduced since this ticket start on host 1 and became much less frequent on host 2, after I switched drivers on it nvidia->nouveau and back.
Also a new laptop showed it, but also rather rarely.
I would second the guess it is KDE specific due to absense of other ideas.
Well, I was unable to spend much time in Gnome to reproduce the effect or refute it.
OTOH it wasn't reproduced since this ticket start on host 1 and became much less frequent on host 2, after I switched drivers on it nvidia->nouveau and back.
Also a new laptop showed it, but also rather rarely.
I would second the guess it is KDE specific due to absense of other ideas.