That is exactly how mine behaves! Once I either put the car into gear, or manually turn the headlight switch to either the on, or parking light position, all goes back to normal.

Yes, this finally fixed my flashing problem. The key breakthrough was that it was the parking lamps and the headlights flashing together. They are on different circuits. I traced the ladder logic with the mechanic (learned that little trick in Engineering school) and that led to the part number listed above (Part # 25762644). Works like a charm. Basically, it was receiving the proper signal, but couldn't decide to turn them on or off. So it did both - really fast!