after updating to UCS 4.2-2 I actualized Nextcloud from version 11 to 12.
I had several groups defined in UMC/LDAP to share folders between users. This has worked fine with Nextcloud 11. In version 12, it seems to me like each user is listed only in one group (looking at the user / group settings in Nextcloud), while the memberships in LDAP are fine.
Users who need to be in more than one group to access shared content don’t see all files.