that's the main reason some racers like myself don't run the car other than on the track. Which is what they are primarily designed for.

I wonder if you are causing enough chassis flex to slam the motor hard back into the mount and weakening it so it breaks on the big jumps.

Running on asphalt or bashing in general seems to be much higher speeds with exponentially greater inertia when you do hit something than on a track. That's a very general statement, but speed multiplies the force of these "few but nothing big" hits IMO.

no offense, but with you being the only person reporting a problem like this with multiple motors makes me think you should look a little more objectively at how you treat your car. If you like to bash and speed run or whatever, and don't get me wrong, im not going to tell you how to enjoy your car, you might want to look at how the motor is positioned and make sure that something can't jam it when it flexes.... I don't know if something under the motor would help or not, it could in theory make it worse if you care causing it to flex. Perhaps find a 90° sensor wire to put on your motor to give it more room between the can and the steering support it could hit when it flexes.

I don't see anything other than chassis flex on hard hits that could cause that to happen to a motor. The motor clearance on these cars is rather tight for most motors. Alum chassis brace might help also.

Edit: just to clarify my intention is not to be insulting or condescending, it's not meant that way. Just trying to get you to think critically about what could be causing this, and how to fix it.