Smart Valve "Ghost Overheating": Reading 30°C while radiator is cold (Need Help!)

Hi everyone,

I’m reaching out because I’m facing a frustrating issue with one of my Netatmo Smart Radiator Valves (part of a 4-valve + 1 Relay setup). I'm hoping someone here has encountered this or found a fix, as it's currently freezing winter and this is happening in my child’s nursery.

The Issue: One specific valve consistently reports a false "Current Temperature" increase. Even after a successful calibration, the temperature reading starts climbing slowly. Within 24 hours, it hits 30°C (86°F), even though the radiator is physically cold and the actual room temperature is much lower.

The Problematic Result: Because the valve "thinks" the room is at 30°C, it stays shut and won't trigger the boiler. Even if I try to set a manual boost, I can't set it higher than the reported 30°C, so the room remains freezing.

What I've tried so far:

• Calibration: Calibrated multiple times with a reference thermometer. It works for a few hours, then starts drifting up again.

• Battery Swap: Used fresh high-quality alkaline batteries.

• Physical Check: The valve body itself isn't warm, so it’s not heat soak from the pipes.

• Isolation: My other 3 valves are working perfectly with the same Relay.

Has anyone seen this "temperature creep" before? Is it a known sensor failure, or is there a way to deep-reset the calibration logic beyond what's in the app?

I've tried contacting support via email but haven't heard back yet. Any advice from the community would be greatly appreciated!

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