Can't change general share options

I can’t change general share option “Restrict users to only share with users in their groups”. When i change it in the gui it will not bee save.
I surch for the the problem that i cant add a group / user to the calendar share list in the calendar app.
I think, perhaps the option in the general share option ist the problem.
I have Nextcloud 12.0.3, calender app 1.5.6 and all apps are updated, the file share app is active.
Thanks for helping

Check my post here Sharing Options