I did get to the freezer fan and found that unplugging it had various effects. Sometimes the clicking would continue, sometimes it would not. Sometimes the rear fan shaft would turn slowly. It was easy to stop with my fingers, which would start the clicking. Sometimes I would plug it back in and it would turn. At times there would be a buzz from the compressor area, followed by one sharp click. Then after a period of silence, the compressor would start up, the rear fan shaft would turn, and the coils would heat up, which I assume is normal operation. Also the door open alarm started working with the freezer fan unplugged.
So it seems that the freezer fan is involved, but there may be other issues. I also realized that I have not checked the ptc relay, I had the wrong part. I can’t get the cover off of the actual ptc relay to check or replace it. I might just buy a new cover so I can be more aggressive without worrying about breaking the plastic. But I sure wish I could find the tabs to unlock it.