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.

I am glad to see these getting moved to torrents finally. Not too long ago I heard a bunch of roms were getting removed from vimms.