My Renault Master had an issue where it constantly showed as open even when I knew it was closed. very irritating as the van beeps at you when you move off and you can't access the trip computer as it says 'Door Open'.
A lot of people try rewiring the brown and white wires in the b pillar which does solve the issue but if you have a bulkhead in place and don't pay much attention to the mirrors then you could easily drive off with the door open.
I had the idea of putting 2 small washers in between the metal guiding thing which brings the door in closer and has solved the issue (for me at least) so give this a try before you start cutting wires.
Good Luck!!
