Can anyone help with a cutting out fault on a Glow worm space saver RF 40/50. Sometimes without any pattern it just refuses to fire up, It can happen when the boiler is hot or cold & I suspect the PCB. Whilst it had cut out tonight I checked the feed from the room thermostat & I had a voltage feedback at the thermostat output, If I disconnected the output wire the feed was only there when the thermostat was turned up (as you would expect) This shows that there is power coming from the boiler to the thermostat when it has failed, Is this the classic sign of PCB failure?