I've been experiencing this issue for years now since kde4. It usually happens when I unplug my laptop, the notification sound will keep looping (playing like 1/2 of sound continuously) until I kill kded5 and restart it. And the only way top kill kded5 is with kill -9. If I logoff it will keep the systemd session alive until I kill it manually with kill -9. Even with systemd's KillUserProcesses=yes.

Is there any way to fix it?