BigIQ How to assign Radius Authenticated user to a User-Goup?

Hello, I got a brand new BigIQ and want to setup rolebased access for some users, who should only manage the Pools what they are responsible for. I could setup that without any problem as long as the users are defined as locally authenticated at the BigIQ. Then I could add them to a user-group and it worked fine... but my idea is to get the users authenticated by Radius. But when I define a user as Radius Authenticated it is no longer possible to assign that user to a User Group. I use BiIQ in Version 5.3.0-0.0.1119 So my question is how can I fix that problem?

Any good tip would be highly appreciated.

Regards Gerhard