I have same side plates, and the same issue,
I have fixed it,
Nothing to do with wires, or door switch etc...
Go on and open the bottom side panel under the steering wheel on driver side, this is that plastic cover and have the fuses behind,
Follow the cable coming from the side panel and find the electric board that manages the side plates
Very small board, sticked to the car with some sort of plastic velcro type thing, which when you take it off you cant put it back in again,
Maybe you can but needs a lot of pressure which may break the board.
There is a small box type of thing on the board.
Keep the door open, and push down on that box with your finger
I like the middle one, but you can use any finger
Walla, you found the problem,
That box is not tight enough to the board.
Not sure what it does, but it is the problem.
I put couple of 5 cents coin on it for constant pressure and used cable tie to wrap around the board.
Use some Velcro to attach to the car
All finished
Mine never played up since
I have spent easy 2 weeks to find out to problem, taken off all the cables, door switches etc....
Hope this helps to you guys