I just observed, that I do no longer get any data from the network. My public IP just changed 30min ago. I checked DNS and it was already pointing to the right new IP.
Check the log of the node and found lots of put error/repair messages + refresh in 8h. Node was shown as online.
Decided to restart the docker container and immediately I got new downloads. Should a new IP not automatically and quickly be identified? Restarting the container everyday seems not to be the solution.