NCP Container does not start properly after reboot

I already tried to find an existing solution in the forum, I hope I did not oversee something.

I am using docker-compose to run Syncthing and NCP in docker containers. But the NCP container does not work anymore. When the system was running, I updated NCP (but noch NC), so while NCP should be up to date, NC is Version 15.x. Before I explain what happened (basically a reboot), here are the logs:

Starting PHP-fpm
/etc/services-enabled.d/010lamp: line 22: php-fpm: command not found
Starting Redis
Starting Cron
Starting Postfix
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2 "No such file or directory")
Init done

Nextcloud and the NCP Interface are both not accessible.

So the story behind that is somewhat complicated. It worked before, and I also made a backup using the NCP Interface. I think that technically I just rebooted the system. But actually I shut it down, booted another system with a different sd card, but the same usb drive. There were containers on this other card, also a NCP container. But it did not use the data on the external drive, but on the sd. Actually, the Syncthing container did use the same data, but it is not broken. I wanted to get some data via scp and then changed back to the original SD card (running dietpi). After that, NCP did not work, with the given error logs.

Any idea how I can fix this? By the way, I use the “External Storage” App to include the Syncthing data as local storage, but that is probably not important I guess. Is it a problem that I try to create a new container which may have a different version of NCP than the one I updated to? I’m a little confused.