I've had one Pittman fail in all the years I've worked on this stuff, and it appeared that it had a motor stall and just burned the armature up. This was on a 3rd Rail steamer with a QSI board. The QSI board was also dead, probably died killing the motor.
I've had three Canon motors croak on Legacy steamers so far, and two of the three destroyed the RCMC for a clean sweep and a big repair bill! I was able to repair the cooked drivers on the third RCMC and save it. All three of the motors exhibited a dead short. I pulled one apart, but I did so much damage getting it apart that I wasn't really able to determine anything about the failure.