Polypipe thermostat not reading room temperature

[John Wilkey]

Hi, Our Polypipe thermostat doesn’t seem to be reading the room temperature correctly. It is working ok, in that it activates the valve but we have to manually reset the temperature each time to activate the underfloor heating. Any suggestions please?

 

[exedon2]

Which model stat? Polypipe have done a number over years.
Maybe a clear picture?