Whirlpool refrigerator keeps freezing up

Refrigerator & Freezer Repair
1

Brand:Whirlpool
Model Number: WRF736SDAM14
Main Symptom: coils freeze up about once a month. changed bad evap. fan motor.
What happens & when: Refrigerator freezes up, thaw last about a month and freezes up again. All stats and defrost heater check out.

Error Code (if any):
Parts or tests already tried: evap. fan motor
Photos / video link:

2

All that is left is the control board that is responsible for putting into a defrost mode. W10854027 Refrigerator Electronic Control Board | Genuine Whirlpool OEM In Stock