os-git-backup wants to delete branch

[Mr. Happy]

Since a couple of weeks I get the following error:

git-backup unknown error, check log for details (remote: remote: Gitea: branch master is the default branch and cannot be deleted To https://git.domain.org/mine/opnsense.git ! [remote rejected] master (pre-receive hook declined) error: failed to push some refs to 'https://git.domain.org/mine/opnsense.git'; )

If I create a new branch, the backup is created successfully but the branch is removed directly afterwards.
Removing and reinstalling did not resolve this.
Anyone got an idea how to fix this?