Would unplugging help melt ice build up in freezer with warm refrigerator?
'sOne possibility is the heater strip that is in the air duct between the freezer and the refrigerator section.  This strip warms the icy air to provide the cold for the top.  If it fails then ice buildup occurs in the duct until it blocks off the air flow and the top gets warm.
When unplugged the ice melts.  If this part failed or it's thermo sensor failed it is a cheap fix (around $30 not including service fees).  I have had this happen on our old GE losing several hundred dollars of food in the refrigerator.
If you put doors on and plug it in and the top gets to the proper level of cold for several days until ice starts building up again you may likely have this issue.
A refrigerator/freezer thermometer is cheap and handy to see what the sections temperatures are really doing, even on a newer digital control unit.