Group runner not picking jobs
Problem
A likely bug that manifests in the UI. The gitlab-runner status indicates "Service is running" and gitlab-runner verify indicates "Verifying runner... is alive" when there is such an error that prevents it from picking jobs.
Background
I have configured 2 jobs runner as group runners, with the same configuration (in particular both can run untagged jobs, and all my jobs are untagged).
On both, gitlab-runner status indicates "Service is running" and gitlab-runner verify indicates "Verifying runner... is alive"
Both appear in the group runners section

The issue is that only the first runner picks up jobs.
It is configured with a concurrency of 5, and when launching more than 5 jobs the others are left pending.
More information about the issue from other customer tickets:
- If the runner is registered on a freshly-created group, it can pick up jobs successfully;
- Resetting runner registration token on the affected group and registering the runner with a new token doesn't fix the issue;
- Disabling all other runners (except the affected one) on the group results in jobs that are stuck and never picked up by the runner.
- Affected GitLab versions:
14.8.0,14.9.1