Gitlab page is not deployed from within group while it is from whithin user namespace

I want to deploy a page for a project which is located within a group. Everything runs without error (the pages job, the build steps, the job reports Uploading artifacts to coordinator... ok) however the page is not deployed. When I check the pipeline I see 1 job, namely pages which succeeded.

When I tried the same with a test project which I've setup under my user namespace then it worked and the page was served. Checking the pipeline there was also one job more - namely pages:deploy which is missing in the group case. This pages:deploy job is also tagged external. Both .gitlab.ci.yml files are similar:

pages:
  stage: deploy
  script:
    # Build the HTML here.
    - mkdir public
    - cp -r build/html/* public/
  artifacts:
    paths:
      - public

Note that I once had a Gitlab page for the group itself. However I deleted this page and I also checked the corresponding URI and got a 404, so I supposed the domain has been freed. Is it possible that there are still some fragments of that old group page in some database which prevent the project page from being deployed?