could be collapsed contacts inside that window switch mate, or in the drivers side switch.
Pull off the switches but connect that regulator and see if it still does it. Its very un-likely the immo is doing it or anything silly from the ecu, it'll just be a grounding wire, a shorted wire or a knackered switch.
Im a diagnostic tech (electronics) and its the most likely answer. The switch has a little see-saw pivot contact that can tip from UP end to DOWN end and returns to the middle. If the tiny plastic pivot mount breaks and the moving contact falls onto the DOWN contact, you get what your experiencing
