"Add Administrator" with SMH

I wanted to add an additional administrator using the SMH-Function “Add Administrator”, and got the following message:
"The group-id of user tamino-admin does not match with the group of administrators for this product"
The problem is that the user ‘tamino-admin’ has the gid of the group “sag”, which the known Administrator also uses, so logically it should work. I’m running Tamino 4.1.4 on Red Hat 7.2.

Thanks in advance.