It seems that at least a partial workaround has been found (at least for me) - if the “Automatic keyboard capture” option is turned off beforehand, the problem with the mouse buttons no longer occurs.
You can find this option in File/Preferences/Input and then uncheck the above setting. Keyboard capture can also be turned on or off also by pressing the RightCtrl key, but unfortunately this does not solve the mouse problem that has already occurred.
Inspiration: https://askubuntu.com/a/1357747