I have a little feedback.
In the meantime I have set up my computer without Proxmox.
The computer is now set up with an Ubuntu 20.04 server and ChannelDVR runs as Docker.
The interruptions in the recording are almost gone.
In the meantime I have also noticed that I can see the following error message on the connected screen:
"ethernet reset adapter unexpectedly" or "e1000e detected hardware unit hang"
So I think that my problem is with the interface settings on my computer.
Nevertheless, I wrote an email to Sillicondust support 17 days ago and have not received an answer to this day. What a shame for such a good product.
Thanks to you for the good support.