Approval rules name can't be blank

Hi,

I am owner in several projects. Today I faced the problem that I get the following error message by creating a merge request in only one of my projects (others are working correctly):

Approval rules name can’t be blank

I also tried to create new approval rules with a name, but I still get the same error.
I am using gitlab.com SaaS.

I compared the working project settings with the one of the failing, but I do not see any difference.

What could be the root cause for this mistake?

I am looking forward receiving your hints.

Best regards

Jan

does anyone have a hint?