KDE does have focus stealing prevention, Have you messed with that at all? https://docs.kde.org/stable5/en/kwin/kcontrol/windowbehaviour/index.html#focus-focusstealing The only thing I can think of is maybe some notification steals the focus and doesnt give it back to the window.

This is a good page to check out if you’re in the market for a new device https://github.com/melontini/bootloader-unlock-wall-of-shame