Diagnosis
The control board is receiving faulty data from a temperature sensor, or the touch panel on the display is ghost-touching. Erratic display indicates sensor failure or a short in the wiring harness.
How to Fix It
Perform a main PCB reset. Unplug the refrigerator from the wall for 10 minutes. This clears any temporary error states. Plug it back in. Immediately set the fresh food compartment to 37°F and the freezer to 0°F. Do not use the 'Power Cool' or 'Power Freeze' features. Monitor for 24 hours. If the settings hold, the issue was a glitch.
If That Didn't Work
A temperature sensor is likely defective. The RS27T5200SR has multiple sensors: fresh food (RT1), freezer (RT2), and evaporator (RT3). A failing sensor sends incorrect resistance values, confusing the board. The fresh food sensor (RT1) is a common culprit for fridge temp fluctuations.
Heads Up
The displayed temperature is an average from sensors, not a real-time reading. It can fluctuate during defrost cycles or after door openings. Use an independent thermometer in a glass of water in the center of the fridge for 24 hours to verify actual temperature.