When launching some game for the first time it sets lower resolution than native.
For example 1024x760 instead of say 1920x1080.
If at native resolution there is a plasmoid at right upper corner, it will be adjusted accordingly for lower resolution.
However, if native resolution is restored, plasmoid will land at the center of the screen.
You might say, it's problem with game, relic from older days. Maybe, but there are far too many titles that do that at first run. Even some 2016 games.

Also related to an old bug which I think should be reopened https://bugs.kde.org/show_bug.cgi?id=152155