My passenger side rear door switch was not making sufficient contact to close most of the time. I ended up putting a bolt into the door facing the switch to make up the difference.
Driving down a trail, it (or perhaps others) will still flicker. Looking at the amount of daylight I can see through the door frames when the van is flexed over rough terrain, I don't think any switch really has a chance. I just flip the interior lights to the off position to deal with this.
'99 EB ex ENG KSWB news van, low rent 4x4 conversion (mostly fixed by now), home built interior.