Upgrade from 14.2 to 15.0 -> missing users and repository link

Hi, after an upgrade of my docker Gitlab CE container 14.2 towards 15.0 using Containrrr/watchtower, I lost all connections to the existing users and repositories.
(docker container runs on my Synology NAS 720+)

Is it possible to fix this? What did I do wrong?

With kind regards,

ErX