Van door contacts

I am getting an intermittent fault on my Ctroen Relay panel which shows a door open warning.  This is said to be "Rear Doors open".  I have checked and rechecked and reclosed and opened and reclosed doors but is still keeps flashing and beeping a warning that the door is open.  It seems to beep and flash when I press the brake pedal but my auto elec says that is coincidence and the fault must be in the contacts themselves.  Any ideas - its driving me nuts!!

could be a bad earth,

bodge fix/first thing I'd try would be a bit of wire wool on the exposed contacts, lightly scour them then liberally spray them with some contact cleaner ,

or WD40 [ or similar ] even if you dont have any contact cleaner to hand.

Check for a broken wire where the loom comes through from pillar to door. 

Thanks guys, I cleaned the contacts at the rear door top which seemed to have had something sprayed on them, and it seems to have worked.  I will go ovr them again to make sure all the crud is removed completely.

Hopefully it won't happens again, and I'll know what to do next time. Ta!