iPad screen sharing not allways working

I regularly need to share the screen of my iPad Pro 11 (iPadOS 14.8.1) with latest Jitsi meet app installed.

On meet.jit.si and on my private Jitsi instance iPad screen sharing just works fine.

But when using the Jitsi instance of our association iPad screen sharing never works. As soon as I start screen sharing the shared screen turns into black.

As I am administrating both Jitsi instances I wonder why the instance of our asscociation fails. It is a cluster with multiple video bridges attached to a central jicofo which otherwise works fine and very stable even under high load. I suppose the issue might be related to the multi videobridge setup and could be a poor configuration but I am out of ideas. I appreciate any hints on this issue.