GV's are having a tendency to stop dead in tracks when hitting hills.  At first this was nice because my gv didn't roll over and or crash.  
exp. cruising dwn a hill at 60 mph (m3) hit the next hill and go from 60 to 0 instantaneously.  IT has happened for all gv so the is not just m3 problem.   
I can't really explain it any better.