Frigidaire Refrigerator Control Board repair

I'm not going to say it's the board because there is always a possibility. however, it's very unlikely. If the board was to fail, then it is going to stay failed. It wouldn't be a yearly thing. The defrost timer is located on the bottom rear of the unit.  It is not located on the board. This part is usually cheap and easy to replace. If you believe this is the issue, then I recommend replacing it. . They hover around $10-$15. Below I have provided a pic that should give you an idea of what you should be looking for. You can retrieve the part number from the original. Try that and let us know the results. Thank you. 

I looked over the diagram in the back and it appears the control board on the door does indeed do it all.

But I also noticed some small patches of verdigris or corrosion on the copper lines coming out from the compressor. While I know that low refrigerant can cause ice buildup in central air units, I would think a working defrost system could be adequate enough to prevent that in a refrigerator/freezer, even in low refrigerant conditions.

The freezer does get overly packed (not my choice), but it was just as packed through most of the 7 years prior to acting up.

I didn't get to do a complete thaw last time, just a hair dryer job on the coil because there was no backup freezer for the food. But there is this time and it has been unplugged for 3 days. I'm half inclined to just plug it back in and monitor it over the next few months. IDK

Thanks for your advice.

Try cleaning those lines and see if it helps. Keep in mind, that if the board is going to fail it would stay failed. Take your time and let us know. We're here to assist. 

This is all that is in the back. Unless the defrost timer is integrated into the compressor relay.

I'm not seeing the picture, but I am aware of what the basic electronic and mechanical defrost timers look like. And I have the freezer pulled out and all that's in the back is the compressor start relay and the run capacitor. There's not even a control board in the back. It makes me wonder if all those functions are integrated into the easily-removable control panel located on the top of the door?

An ordinary freezer would be easy, but these odd Electrolux models are throwing me for a loop.

I do believe it would have taken several months to began icing up the coil and the airways, especially in the winter. The first incident was late-summer and cold weather came soon after.

This is an upright freezer with electronic controls on the door.