you'll want to check your D1R and D1L diode block circuits,
could be a faulty armature diode , these would be located between the H-Bridge board and the IGBT's mounted on the heatsink assy.

i would also check the diodes on the drive board assy underneath the logic card. if any are burned you'll need to replace the board.

while in there check for any corrosion around the H-Bridge board thats mounted on the heatsink under the drive board, sometimes moisture can get in there and corrode up and cause problems in that area.