Question about Netatmo Starter Kit Smart Radiator Valves Advantage Set

Has anyone had the same experience with the "True Temperature" function not working? The actual value temperature is constantly drifting away in my living room (with three valves). The deviation is usually 1.6°C and cannot be corrected by anything. Separate measurement is done by a Netatmo indoor module, which disappointingly cannot be used as measurement for the thermostat valves.