GE Refrigerator w/Bottom freezer cooling issue

I have a GE Profile fridge w-bottom freezer where the fridge compartment gets warm (50-65 F). The freezer goes up to ~8-10F and usually is ~0. This is intermittent and happens every 6-12 months. Changed motherboard, did not fix. The only resolution is unplugging for 12-24 hours. Could a sensor (thermistor?) be icing over or maybe the damper is not opening? Please advise before I bring it to the landfill, thanks…