Hello there, i have an appollo fanfare 15/30si boiler which i am experiencing problems with.The boiler will start when prompted from the room thermostat but occasionly it needs the outer casing of the boiler to be given a little tap , it will run for approx 1hr then stop ,it seems like something is stuck slightly , it will not restart untill it has cooled and then will restart when given a small knock on the casing again ?, when running it runs smoothly and heats both radiators and hot water tank ,any ideas please, regards, Steve.