If cooling unit had a leak it would not chase ambient air temps (warm up/cool down as temps change) it would quit cooling
Unplugging thermistor SHOULD cause fridge to run continuously and result in freezer temps 0*F or lower and food compartment temps 38*F or colder......unplug at lower board P2 connector (left side) and run fridge overnight measuring temps with bulb thermometer in glass of water
Other test .......unplug heater element leads from lower circuit board and plug them directly into 120V AC outlet...run fridge at least 12 hrs
This will bypass all controls and test cooling units ability to cool.
Otherwise cooling unit is slowly dying due to obstructions/blockages inside the cooling unit
A refer that chases the out-side temperature is improperly vented or has a weak cooling unit
