That was actually a good keyword and I’m annoyed that I didn’t come up with it on my own.
I swapped Yoast for Rankmath. Rankmath has its own role system. That was deactivated. But I activated that and granted this role 2 rights over the Rankmath rights system and now it works again. The devil is sometimes really in the detail. 😉
Many thanks again for the common error search and the great teamwork. (: