That problem is most probably caused by corroded splices in the wiring harness. Not immediately obvious after opening the door. I posted before on this issue. Door card is relatively straightforward. Some small screws, most hidden, pull off window switch, unclip inner door handle rods, be careful of upper armrest part which is hooked in, pull panel to unclip it. The non-m panel comes off in one piece including the carpet contrary to the video which shows an M. A special tool helps for this. Watch for speaker wires when undoing the panel.
Did you reset the Door ECU? If you did not, search for the procedure on here. I have had to do it on my 456. Very simple..... Scott
