2012 1.2tdi Greenline Fabia II. Keeps throwing up the fault code P008700. Coil/glow plug light flashes for the remainder of the journey but resets when you come to start the car again. Does not go into limp mode and is intermittent. Changed fuel filter, in tank lift pump, fuel rail, fuel rail pressure sensor and fuel rail pressure regulator, but still appears periodically. Any suggestions as to the cause or other courses of action to try and eliminate this issue. Thanks