Rock crushers? As in big yellow conconstruction truck.
I was thinking this was in a car.
OK is it still a 12 volt system?
Is there a lot of dust?
How hot do the hydraulics on that thing get?
New theory;
Dust something else stalls the motor, the Hydralics heat up, the ambent temp goes up, insulation on the wire in the coil melts, coils short out and the hole thing heats up to the melting point.
it may be posible for the coils to be made of cheep Chinese copper that has a higher resistance and lower melting point.
Just some thoughts, Andy