Pull mirroring error

We use GitLab pull mirroring to keep some repositories in sync from GitHub. As of two days ago several of those mirrors are failing with the error:

The mirror user is not allowed to push code to all branches on this project.

The repositories we are mirroring that are public on Github and do not require authentication continue to work fine. For projects that are private we are providing credentials for mirroring and they receive the error noted above. I know you can no longer configure these mirrors without a license but I am not sure why they suddenly stopped working.

Is there something we can change to get them to work again?