[3.0.0 stable!] default style function doesn't work

Don't know why and I think it didn't happen in former versions but I can't change default style.

Once it was set, any changes through the backend don't change anything. The only way to change the default style is to delete the style which is shown when a not logged in user / guest visits the board and then choose a style to replace the deleted.

The function to define a default style - which afterwards display the default style in the backend with a "*" doesn't work for me.

Also checked the database entry. prefix_config => "default_style" is set correctly. Which means the ID is the one I chose in the backend - but guests don't see that style as default.