I already tried lots of things (reboot, different port, different containers, prune, ...) but it does not work. The port is not shown as used.

So this is my problem: I am running a NAS with Unraid. I have some docker containers installed: Immich via docker compose, pihole as a normal docker container and some more. However, most stopped working. PiHole and Immich are still good, but when I try to start others - no matter if "old" or newly installed -, I always get the error message "docker: Error response from daemon: Address already in use.".

This is an example run command with its output:

$ docker run -d --name docker-test -p 5811:80 nginx
Unable to find image 'nginx:latest' locally
latest: Pulling from library/nginx
02d7611c4eae: Pull complete 
589066960983: Pull complete 
7674eff4effe: Pull complete 
2e964620d7d0: Pull complete 
24ca5634560a: Pull complete 
f7f0a5b0f147: Pull complete 
964234ddf75f: Pull complete 
Digest: sha256:7272239bd21472f311aa3e86a85fdca0f1ad648995f983ab6e5e7dea665cd233
Status: Downloaded newer image for nginx:latest
22d914edf556ca5a599ea35146ad59fbf5e2aba9f76996ec41e8d7b42d82240b
docker: Error response from daemon: Address already in use.

I never started an nginx container before. Same output with the container I actually want.

Checking the port with sudo netstat -tulpn | grep 5811 or lsof -i | grep 5811 does not give any result. Pruning the docker networks, reboots, ... all did not help. Trying other random ports neither.

What else can I do? What could be the problem, where to look for it?