I originally reported getting this warning x 2, coming down a hill.  I thought maybe the battery was overheating by overcharging in Slope Assist Mode.  However, today, after driving normally and after the car was turned off and parked, I received a remote message saying that there is a warning light on.  I went back to the car, and it was the same "stop safely now" warning, and the car could not start properly.  As before, after ~ 5 minutes, I was again able to start the car normally.  The last