Hi, Kai!
Welcome to Microsoft's Community.
After doing some research, we found that there is another thread open regarding the same matter. With that said, we will proceed to close and lock this thread, but please rest assured we will continue looking into the situation you are experiencing at the moment.
The public thread will be blocked. Please reference to the other interaction: Could you please change the Legal Name in my Certification Profile? - Training, Certification, and Program Support (microsoft.com)
We hope you have an amazing week,