2001 E53 X5 Passenger door open alert, even when closed

[shedtastic]

So it started intermittently: the chime warning for 'door open' plus the interior lights would come on briefly on left hand bends. The dash showed it was the passenger (right hand side) door that was opening enough to trigger the sensor. As soon as the corner was completed the dash indication would go off again.

I thought it might be something I could adjust out, but of course I put it off.

Well, now the door either claims to be open the whole time or (worse) constantly triggering the chime and interior lights.
Some basic googling seems to show that the microswitch is inside the door lock actuator mechanism - and I'd really rather not have to replace that. Is there some method of adjustment I can try? or is there any chance that silicone spray shot in any available aperture of the mech will help?