Symptoms: Claw will not move left or right. When power is applied, the stepper motor will just hold the claw in its current position. You can manually move the claw without power, but when power is applied it stays in that position.
Procedure: After replacing the “wrench” motor, I realized the defective motor had damaged the motor control board. More specifically R9 (10 ohm / 2 watt) resister. This board also has a separate circuit that controls the direction of the claw movement. I had left that wire harness off when reinstalling this board. Reconnected this harness to correct the failure.