Kenmore refrigerator weak cooling no error code

Hi, I have a Kenmore refrigerator model# 795.71303.012. It started intermittently causing a minor soft ice cream issue in the bottom freezer compartment. Now it will not maintain the required 0°F temps anymore. So I put Taylor refrigerator thermometers (1 each) in both the upper and lower compartments. The upper refrigerator section will not go below 40°F even if I set it to the lowest temp setting which is 33°F. The lower freezer section will not go below 28°F even when setting it to the lowest setting which is -6°F.

I have cleaned the condenser section which was quite dirty but not completely clogged. I carefully vacuumed and cleaned stuck on films from the fan blade & condenser coils. The refrigerant suction temp is cool going into the compressor and very warm descarging out of the compressor. I see no components that seem to have any issues running and activating, etc.

I have not pulled interior panels yet since I hear the evaporator fan running and feel the airflow coming from the top center vent opening at rear of the freezer section.

I found the tech info sheet below the front underside of the unit and tried the panel display test and the push button PCB test as instructed there. Both test showed no error codes.

As far as I can tell, it has been running continually since the problem became consistant. There does seem to bee a high frequency sound I believe coming from the compressor, but not overly alarming in volume level.

I am an HVAC technician with extensive background knowledge but need help with someone who can help me complete this diagnosis and repair it myself.

Please advise with my sincere respect and appreciation, Randall