maybe this problem: https://github.com/nextcloud/server/pull/20039/files
And see here: LDAP groups found but not showing up in users
After doing the fix in the first link it is working for me 
BR
Michael
maybe this problem: https://github.com/nextcloud/server/pull/20039/files
And see here: LDAP groups found but not showing up in users
After doing the fix in the first link it is working for me
BR
Michael