I've had this on exactly that boiler size and model and it turned out to be a PCB fault. It looked like brackets turned through 45degree. Speak to technical support they can take you through a factory reset of the board software which may or may not iron this out, they called it a software glitch initially. Ironically the fan did not run anymore following the fitment of the upgraded replacement PCB. The fan may have been the original cause of the board fault though. Turned out expensive.