Whirlpool bottom freezer Refrigerator not cooling but freezer is frosting over

Whirlpool Refrigerator Model GB2SHDXTS02 S/N KY1331093. Refrigerator section does not cool but bottom freezer is cooling and making ice but is freezing up. I have replaced the capacitor, the control (jazz) board, and most recently, the damper assembly control. The damper was damaged but that was not the issue apparently! I am pretty sure the evaporator fan/motor is working but I am aware that it could be the thermistor or the bimetal defrost. We have a borrowed fridge that has its own problems and won't last much longer!