Hi Georg
I found a separate issue that I have raised an incident for.
I could assign the restriction to the business role, yet when I checked the users authorisation I noticed that the new authorisations had NOT copied across from the business role even though the update was complete and the business user was assigned.
I did a temporary fix by click 'edit without business roles' of the user and clicking 'Copy from business role' and everything updated correctly.
Sounds like you may have the same issue.
PS. Looks like you have done everything the same as I did and mines working once I copied the authorizations across.
Cheers
Brad