Push rule for branch name blocks matching names

Describe your question in as much detail as possible:

I have set up a push rule for the branch names on project-level. I am using the following regex: /(feat|docs|ops|fix)\/[a-z]{2,}[a-z0-9-]{0,}?[a-z0-9]$/g. Tools like RegExr prove that the expression matches names like ops/codeowners.

Nevertheless, when I try to push to either to an existing branch or creating a new branch on remote (via push), I get the following error message (path obscured):

 ! [remote rejected] ops/codeowners -> ops/codeowners (pre-receive hook declined)
error: failed to push some refs to 'REMOTE_ADDRESS:group/subgroup/project.git'

I hope you guys can help me!