Bottom Freezer Refrigerator compressor runs for a while then stops cooling

My Bottom Freezer refrigerator stopped cooling a few weeks ago. I checked the compressor compartment and the fan is still running. The compressor relay and capacitor tested OK (resistance btwn 5-10). The compressor also checks out OK. I tested the defrost timer (turning clockwise) and that does not seem to be the problem either. I then opened up the freezer compartment and tested the temperature control thermostat. I tested resistance while it was OFF…and no reading as expected. The tested it ON and it made sound, indicating a connection…so this was also tested OK. The final test I did was to test the Defrost Thermostat. I disconnected it and placed it into a cup of ice cold water for a few minutes and tested the resistance again (Ohms). The ohmmeter should sound (resistance) when I tested it in the cold water, but no sound, and no reading, indicating an issue. I did the test numerous times and same result. Lastly, today, while the defrost thermostat was unplugged and I had the refrigerator open (ice tray disconnected, defrost thermostat disconnected), I plugged the refrigerator into the outlet and the compressor came on and it started to freeze again. My question is this, could a bad defrost timer prevent the compressor from starting, even though my freezer didn’t have a froze over problem? I searched all over the web and all advice pointed to a bad relay or temperature control thermostat. But both (all) of these tested OK. I ordered a defrost timer because I concluded it was bad anyway. I unplugged the refrigerator again and left it off. Again, what else am I missing here?

Your response is kindly appreciated.

Regards