[FrankJ]

Measure the current to the motor. Knowing the current & voltage going to the motor & the motor curve you can get a good guess of speed. Free running at anything more the %70 of stall torque amps is cause for concern.

Maybe you have too much compression on the ball? When the ball hits the shooter does it stall the motor & it is inertia loading that is killing the motor?

The FP are pretty durable. They take a lot of abuse. Holding them full power at stall for any length of time would be abusive.

If you run thru the PD board, the CB will give you a little protection from burning up the motor.