@C-Beats
The error is gone, I can change themes now. But as soon as I go to options Bigbox crashes completely.
With the default theme I get the error message even if I select a system.
But it must be the language German, I switch to English, it works without problems.
My Repsekt for the quick bug fix
I have created a video to help
unknown_2022_07.21-19_13.mp4