Merge not possible

Summary

If we create a new merge request for some reason the merge is disabled once we resolve "the items" above. But we can't get it into this stage because we can't figure out what needs to be fixed.

(Summarize the bug encountered concisely)

Steps to reproduce

For this project (privately hosted) this is the case for every new merge request.

What is the current bug behavior?

Merge not possible

What is the expected correct behavior?

Merge should be possible.

Relevant logs and/or screenshots

We are running GitLab 11.10-ee