[Noob] Internal Networking errors... I suppose

Hi, I got a weird plethora of problems with containers not communicating with each other or being unreachable despite running.

What happened?

• I had growing problems, especially with my nextcloud container which got less and less stable.

• This probably led to a corrupted docker.img file because I stored it on an HDD with the wrong format (at least that was what was explained to me).

• I I scraped the faulty one, assigned an SSD to the cache where the new docker.img is now located.

What are the problems now?

• First a smaller one: Krusader and qBitTorrent, which both use Port 8080 for their WebGUI out of the box, are also causing me problems: When I rebuilt the docker.img I used the templates from before, where I've already set Krusader to port 8081, which worked fine until the crash. Now when I start them and try to get into their WebGUI, both send me into a noVNC instance (I have no VMs activated?), which seems to try to connect me with Krusader. qBitTorrent is unreachable for me, because I always get sent to the noVNC page.

• Now my main problems: The nextcloud container is unreachable through WebGUI and through desktop app. Connection is simply timing out. The nextcloud.log isn't helping me, since it's last entries are from a few days ago, right before the docker.img crashed.

• When I look into the container log, the only error I can see is a connection problem to the MariaDB. The MariaDB container is running and the logs are not showing any connectivity issues per se as far as I can see. But still, I can't even ping MariaDB from nextcloud's console - it simply times out. When I ping it from the Unraid console, everything works fine.

• My vaultwarden container is also unreachable, but I haven't investigated further into this one yet.

• Other containers (e. g. Jellyfin, Jellyseerr, Teamspeak 3, ...) are running fine.

What have I already tried?

• Multiple server reboots, docker.img rebuilds, turning docker off and on again...

• I have moved nextcloud, MariaDB and Redis into a custom network.

• I have set the nextcloud's /data share permissions.

• I have tweaked the nextcloud's config.php.

• I have checked the port mapping of the ports in question.

That's as far as I got with my own research and asking AI. Unfortunately I'm a full noob and maybe someone knows what's up ^^". I've attached my mariadb-error.log since that is the only one with information regarding my current situation.

mariadb-error.log