there is thermal shutdown circuit in the motor. If it is
hot, it won't run....

Might be that the pin holding the sprocket to the
gears has broken... The gears would spin,
but the sprocket is loose on the shaft.

Open it and see what the problem is. They
are simple machines.

electronics:
You have 1)R/C circuits (remote control)
2) motor driver
3) limit switches.

mechanics:
motor,
gear box,
sprocket, chain

The limit switches are connected
to the gear box.

Rich