Get 404 when trying to create the pull request, change set does not exist

When I edit a page and then try to publish, I get a 404 with the message:

The changeset 'humenidp-edit-77f2fdc9441' does not exist in repository 'ams'

If I go back to the screen to submit the pull request, I can see there is a commit and the commit does exist, it does not belong to a branch (I think that is supposed to happen?).