UCS5: Active Directory Sync does not work

Hello,

i set up Active Directory Sync, but if my Windows AD Server is not reachable i can not auth against my UCS (synced?) .

I would have expected it to still work since i want to back up my Windows AD with a UCS Slave/sync.

I can see all the users with univention-ldapsearch.
As well as:

id testuser

uid=2009(testuser) gid=5001(Domänen-Benutzer) groups=5001(Domänen-Benutzer)

… just the (Web-)Authentification does not work. :-/

Cheers,
Michael