Never had any problems with it crashing or hanging. But just to let you know Im use Cubase AI 9.0.30 (the one that is free and includes Groove Agent SE) and it works fine with Groove Agent 4 and the Simon Phillips addon. Don’t think there is any real need to upgrade if your a drummer.
Just a couple of bugs in Groove Agent though that support are looking into:
a) Ride cymbal not choking.
b) when you load a kit with “Load Kit with Patterns” in the Kit slot, deselect it and load the same kit again it still loads it with patterns.