Changing "CI/CD for external repos” created mirror repo from "private" to "public" leaves it in bad state

Description of the problem

Accessing Settings/Repository of a GitLab project which is a "mirror" of a GitHub repo results in a 500 error page.

Also all webhook events sent by GitHub error out with 500 {"message":"500 Internal Server Error"}

Which Group/Project (with full path) is experiencing the issue?

https://gitlab.com/ivailop-mirror-crash/mirror-crash

Approximate date/time when the error occurred.

I noticed it on 2020-04-01 when I changed the Group and Project privacy to public.

I guess the problem might have existed before...

Describe what you were doing right before the issue occurred.

Without knowing that our Group (https://gitlab.com/s2technologies) was private I create a new Project, via "CI/CD for external repos” - a "mirror" of a GitHub public repo.

Due to The free period of CI/CD for GitHub is ending soon since 2020-03-23 we started getting 400 errors. Realizing they might be related to the fact that our GitLab Group was private I changed it and the mentioned above Project to public.

After changing the Group and the Project privacy to public we started getting 500 errors on:

• accessing the Project's Settings/Repository
• GitHub webhook events' response