Cafe fridge defrost issues

Freezer keeps frosting up.

I have a cwe19sp4nnw2 CAFE counter depth french door fridge over freezer w/o exterior water or ice maker. I can't find any service manual or mini manual for this fridge maybe because it is counterdepth? I also can't figure out if there is a diagnostic mode or how to access it. Most GE fridges use the external ice maker controls to enter diagnostic mode but I do not have that on mine.

The fridge started making a lot of noise and it turned out that the evaporator fan was rubbing on some ice that was built up on the condenser. I defrosted it but a few weeks later the same thing happened again. I again defrosted it and tested the defrost heater, and it looks good (non open, I forget the exact resistance but it was less than 100ohms I believe).

A couple weeks later I noticed some stuff on the top shelf of the fridge was frozen, then a week after that the fridge was room temperature but the freezer was still cold. I opened it up again expecting the damper to be the issue but the damper was open, no air was coming out of the vent from the freezer. So I again open up the freezer back panel to find that the evaporator is frozen solid. I defrosted it again to buy me some time to figure out what the real problem is. I know there is a defrost thermostat and maybe a defrost switch or timer but I am unsure where all of these components are and how to test these to know if they are bad.

If anyone has a manual with wiring diagrams and diagnostic mode info I would really appreciate it. Or if anyone has any pointers as to next steps, I could use all the help I can get!

Thank you, I will check this. I heard that the thermostat might only be for runaway conditions on this model and I should check the temperature sensor. I will check both next time I open it up.