Can't move a project and also can't create a project with that new name

It seems like I tricked gitlab in a kind of transient state.

I want to rename (changing path of) a project. If I try to do that I get a HTTP 500 error. If I instead try to create a new project under the desired name I get this error in the GUI:

The form contains the following error:
Name has already been taken

I guess I confused gitlab somehow. Maybe an admin can look at it in the backend and fix it for me?

My desired action is to rename gitlab.com/wired_/ansible/rack.pizza_ansible to gitlab.com/wired_/ansible/rack.pizza.