36v20 Motor Driver problems with FF2 and RESET

Hello, I have recently used a Pololu 36V20 motor driver with my brushed DC motor.
I used it with PWM (from Arduino Uno board) connected to PHASE input, PWML not connected and PWMH directly connected to 5v of the driver regulated voltage. CS was excluded.
I used a 50% Duty Cycle for motor Stop , 95% for max forward, 5% for max backward and everything worked fine during tests. The only strange thing was that every time I powerd the driver (24VDC) FF1 was low but FF2 was high, so I needed to reset it by an external switch directly connected to the driver GND pin, but this was not a real problem for me because after this first reset only at power on, the driver worked fine.
Yesterday, I noticed that the driver was not resettable by the switch: FF2 pin is high at +4.94V and FF1 is low and in this condition the driver is not able to drive motor.
This happened just after I have put all the system inside an aluminum case, could it be a ground loop problem ?
What could be happened ? How can I solve the problem ?
Thanks for the answer !


As specified by the high-power motor driver 36v20 product page, a fault condition flagged by FF1 being low and FF2 being high indicates a short circuit. Has the fault always happened after powering up the driver? Could you post a picture showing your motor driver in your system, including the aluminum case? Also, could you post close-up pictures of both sides of the motor driver board?