Brave profile is locked

The Problem

Brave won't start.

The Analysis

journalctl -f shows:

Jun 10 09:26:37 localhost.localdomain systemd[2802]: Started Brave Web Browser - Web Browser.
Jun 10 09:26:37 localhost.localdomain plasmashell[10126]: [10127:10127:0610/092637.870391:ERROR:process_singleton_posix.cc(353)] The profile appears to be in use by another Brave process (8779) on another computer (linux.fritz.box). Brave has locked the profile so that it doesn't get corrupted. If you are sure no other processes are using this profile, you can unlock the profile and relaunch Brave.
Jun 10 09:26:37 localhost.localdomain plasmashell[10126]: [10127:10127:0610/092637.870519:ERROR:message_box_dialog.cc(146)] Unable to show a dialog outside the UI thread message loop: Brave - The profile appears to be in use by another Brave process (8779) on another computer (linux.fritz.box). Brave has locked the profile so that it doesn't get corrupted. If you are sure no other processes are using this profile, you can unlock the profile and relaunch Brave.

The Solution

heiko@localhost:~> find . -iname SingletonLock
./.config/Signal/SingletonLock
./.config/google-chrome/SingletonLock
./.config/BraveSoftware/Brave-Browser/SingletonLock
heiko@localhost:~> rm ./.config/BraveSoftware/Brave-Browser/SingletonLock
heiko@localhost:~>