[Qbranch]

The aforementioned insights provided are probably your most likely bets, but also check to make sure that your burning hot motors have intact o-rings around the ends of their casings (places where the black painted portion of the CIM meets it's two cast endcaps).

Missing or damaged o-rings can allow fine particlates into the interior of your motor and degrate or destroy the brushes in your motor. From there, it's possible that you rmotor could be partially or completely shorted out.

-q