Docker Proxy for registry.gitlab.com not working

I’m trying to configure Nexus with a Docker Proxy for registry.gitlab.com to proxy the gitlab-runner-helper image (registry.gitlab.com/gitlab-org/gitlab-runner/gitlab-runner-helper:x86_64-dcfb4b66) - but an error appears in the Nexus log:

anonymous org.sonatype.nexus.repository.docker.internal.auth.BearerScheme - Failed to retrieve docker bearer token
2023-05-25 15:25:00,394+0200 WARN  [qtp702342186-465944]  anonymous org.apache.http.impl.auth.HttpAuthenticator - BEARER [complete=true] authentication error: Could not retrieve token from https://gitlab.com/jwt/auth. Status code: 403

I do have the Docker Bearer Token realm enabled.

Proxying works for so many other registries, but this one seems to fail. What am I missing?

My cross post from the GitLab forum: https://forum.gitlab.com/t/registry-gitlab-com-not-working-in-docker-proxy-of-nexus-repository/87118

It looks like Gitlab is returning 403 on authentication, you’d need to figure out why