Your boiler is struggling to talk to your wireless thermostat, meaning it doesn't know when to turn your heating on or off.

DIY fix possible

Check if the batteries in your wireless room thermostat are flat and replace them if necessary.Ensure the thermostat is within range of the boiler and has not been moved behind a large metal object or thick wall.Follow your specific model's manual instructions to re-sync or 'pair' the thermostat to the boiler receiver.