I called out a repairman who used a laptop to troubleshoot. He charged me $119 just to come out. He told me that the control board wasn't telling the evaporator to periodically defrost and I noticed that it was encased in ice. Then, he gave me an estimate of $400 to replace the board. Breaking down the estimate, that would be $200 for labor, about 30 minutes, and another $200 for the board, however, he didn't have a replacement board in stock. Knowing that I could replace the board myself, I was happy to order the board from PartSelect and save on the $200 labor charge.
Fridge and freezer were not keeping proper temp (freezer would get too cold, fridge too warm), as the cooling coils were icing over and needed manual defrosting; it was not going thru the automatic defrost cycle. Changed out the defrost heating element, thermostat, and two temp sensors, none of that worked. It was this part (main board) that was the culprit. Eight wire harnesses to undo and re-hook, one was hard to pull out but it came out. Read and follow the anti-static instructions. To make sure, I grounded my hand with a copper bracelet that was grounded with a copper wire to the metal chassis of the fridge. I also drew out a rough sketch of the connections and numbered them all with a black fine tipped felt marker before undoing them. This finally fixed the problem.