Bonne's (as you can see by my sig, I know a thing or two about them) can be tempermental about electrical. Much more than a GP. Because everything on them sucked electrical like they had their own nuclear generating plant. So yes..the ground busses by both front drivers doors could get wet and corrode easily. Another thing I found on my Bonne was even though the battery cables were tight, if you pulled the bolts out and pulled the cover off the end of the cable..corrosion was pretty common there. That can cause lots of issues as it's the electrical of the car.
The light flicker shouldn't happen when the engine stalls. keep in mind..I'm saying "shouldn't". As you know it's tough to diagnose when you haven't experienced it.
