GE Bottom Freezer Icing Evaporator

Model GBS22HCPAWW bottom freezer.
Evaporator ices up. After defrosting the unit and plugging it back in, it ices up again in 2-3 days.
Tried manually defrosting using the pins on the motherboard (LINE and DEFROST). The unit begins defrosting, but the compressor inevitably starts up and tries refrigerating while I'm manually defrosting. This seems foreign to me. Shouldn't the compressor remain off, while the motherboard is jumpered, and only start up when the jumper is removed?
Since the defrost circuit does what it's supposed to do, would the motherboard be suspect? I don't want to spend gobs of money on a motherboard and find there's some other problem I hadn't thought about. Thanks for any help you can give me.

When the board is jump out, the refrigerator should be in the off position.

If the defrost system works fine when jumped then the board on the back of the refrigerator isn't telling the machine to go into defrost when its supposed to. The board would be the problem..... However......

For the refrigerator to be icing up in 2-3 days, thats too quick. I would be checking door gaskets or making sure the doors are closing correctly. If the machine has an ice and water dispenser make sure the ice shut flap isn't stuck open(where the ice comes from the door)

If there is no dispenser in the door but you have an ice maker in the freezer, make sure its working correctly. If you don't have water running to the ice maker, turn it off.

Let me know how you made out with your fridge.