I have had mixed results with AirGroup in the GUI, as well. I'm running 8.x code. The latest 8.3 code is much better than the 8.2 code for this.
As far as I've gathered, the latest information the controllers have gathered about the client is what gets "stuck" in some of the smart features, such as AirGroup.
Actually, I made a change in AirGroup the other day to block more things, but all the clients who WERE "AirGroup servers" for that particular string were stuck in the GUI until they disconnected and reconnected (thus giving the controllers new information about themselves). We verified this as a workaround by manually rebooting laptops and issuing a CoA and watching the GUI update itself.
I don't like it is a solution, but that's our "work around" so far. Because of little things like this, we usually make bigger changes on Friday so that caches are cleared etc for a clean Monday.
iann