Replication issue between ucs & ADDC

Hello guys
we have a problem with replication (sync) between
UCS 4.4-8 and AD DC 2016 / 2019. I hope you can help me.

We have 4 DCs.
UCS is joined to DC und is member of the domain controller.
The replication works only if the “connector/ad/ldap/host” under “Univention Configuration Registry”
points to “dc1.domain.com”.
If we change the ldap hosts to other DCs e.g. dc2.domin.com
replication of objects and attributes from AD to UCS does not work anymore.
E.g. when we create or delete a user.

DNS works from all sites, UCS server is trusted on all DC.
We do not see any error in the following logs:

  • connector.log
  • connector-status.log
  • directory-logger.log
  • check_join_status.log
  • listener.log
  • system-stats.log

Does anyone know what is the problem here?