The door only lowers if the button on the wall is held in until the door is all the way down. The flashing light code points to the beam sensor. The light on the receiver comes on when the beam is aligned and goes out and beeps when the light is blocked. There is 12 VDC where the beam sensor wiring connects to the back of the motor control box with the light beam blocked or not blocked. Should this voltage change when the beam is broken?