Strange UNC DNS issue

I’ve a strange issue, all internet connection works so far I can see correctly.
I can visit each website from my clients without an issue.
But around the half off my Radio stations didn’t work, and show me only the status buffering.
As soon I change the client DNS settings from my Univention DC, to
All radio stations works as well!

Any Idea how I can solve this issue?

I’d start to check whether your UCS can resolve the domains in question. Tools like dig (see ) and nslookup on machines where “dig” is not available can help.
If there are failures in name resolution it is necessary to know about the configuration of the DNS-backend (UCRV “dns/backend”, see and the forwarder settings (UCRV “dns/forwarder1” to “dns/forwarder3”, see

Thanks for your support the dns forwarder was the issue.