Problems restoring GitLab from a backup

Describe your question in as much detail as possible:
I’m running a GitLab 12.3.5 (with Mattermost). Prior to upgrading i’d like to check if i’m able to backup and restore. So i’ve build up a test system, also 12.3.5. While backing up and restoring Mattermost works, it fails for GitLab itself. My Gitlab is running on a VM. The VM is snapshotted on a weekly basis. I used the following approach:

  • created a Git repo and pushed it to my GitLab, so this is version 1 state

  • after the weekly VM snapshot (which now contains version 1), pushed some changes so this is version 2.

  • did everything mentioned in the docs to create a backup, so i have a xxx_2020_08_18_12.3.5_gitlab_backup.tar which now contain version 2 and stored the config files

  • shut down my VM and recreated it from the weekly VM snapshot, so this contains version 1 again

  • did everything mentiones in the docs to restore from my xxx_2020_08_18_12.3.5_gitlab_backup.tar and the config files

  • What are you seeing, and how does it differ from what you expect to see?
    After these steps the GitLab repo still contain version 1 data.

My guess is: this is because the GitLab im restoring to is not ‘empty’, because i use the weekly VM snapshot instead of a blank new GitLab?

No one? I’d really appreciate help in this case. Is my question somehow unclear?