Diagnosis
The thermostat's internal temperature sensor is being influenced by a local heat source or improper placement.
How to Fix It
Check the thermostat's environment. It must not be in direct sunlight, placed on an exterior wall, directly above a heat register, or near electronics that generate heat (like a router or AV equipment). Relocate it to an interior wall if necessary.
If That Didn't Work
You can calibrate the displayed temperature. Navigate to Menu > Preferences > Temperature Offset. Use a trusted, calibrated thermometer in the same location. Adjust the offset in 0.5°F increments to match.
Heads Up
The remote room sensors are the primary source for temperature averaging. If using sensors, ensure the thermostat itself is excluded from the averaging calculation in Menu > Comfort Control > Participation.