Hey NowAge!
I managed to solve this issue easily by heading to the form settings of the “broken” form.
I noticed that the German translation of check box (“Kontrollk?stchen”) was selected as the input type and that right below this there was an option called “checkbox-multiple”. After I selected this one and saved the settings that ugly error message was gone! ??
Hope that helps!
Cheers
PS: The error was visible right above the check-boxes on
https://www.craftkammer.com/kostenlose-beratung/
Now they’re gone as you can see easily ??