I think was Jrjava was trying to say was
It’s it possible you accidentally installed a 2nd rubber bumper’s into the motor shaft?
It would be an easy rookie mistake. Pull the motor and make sure you only have 1 if your motor was Hot. I found that when I drove slow and up steep hills it made lots of heat.
Could it be that it need’ed a speedy run on the flats to cool off. My other cars that I would run for a extended periods all needed cool air kits
Vents , fans , controller heat sinks
More info on the cool air kits