ADDITIONAL_HOSTS stopped working, showing "503 Service Temporarily Unavailable"

Instead of seeing the OK response from the container via the domain assigned in ADDITIONAL_HOSTS as usual, now we’ve started seeing
“503 Service Temporarily Unavailable

The automatically generated domain by Kubernetes continues working however.

The additional hosts domain points as CNAME to currently working domain
Any ideas?

  • What version are you on? Are you using self-managed or
    • *GitLab (Hint: /help):
    • *Runner (Hint: /admin/runners):kubernetes runners, latest version

Deleting and recreating the cluster has solved the problem