The update to version 5.19.5-3 resolved the issue.
- Bug#974135: kwin-x11: Logging in to KDE X11 fro... Silvério Santos
- Bug#974135: (no subject) Silvério Santos
- Bug#974135: marked as done (kwin-x11: Logg... Debian Bug Tracking System
The update to version 5.19.5-3 resolved the issue.