GE refrigerator not defrosting

Refrigerator & Freezer Repair
1

Brand:GE
Model Number: PSHS6PGZBESS
Main Symptom: freezer evaporator ices up, freezer and fresh food sides both to warm
What happens & when: both side too warm

Error Code (if any):
Parts or tests already tried: : removed the defrost heater and tested ok, 22 ohms. Defrost temp sensor is closed. Evaporator and condenser fan both run ok. Is there a defrost timer or other part that could be the problem
Photos / video link:

2

If the thermistor, heater and bimetal are all good then this will be a faulty main control board.