Our 1290 thermostat (which is paired with a Micro WPS) is not holding temperature. When the sample tray is in and the temperature is set at 4°, the actual is 10°. If I pull the tray out, the actual drops to 7°. I used a kimwipe to determine that the fans are running. I vacuumed the vent slots, so they are not clogged. Is there any way I can repair the thermostat or do we ned to buy a new one?