One, the door switch is cheap and unreliable. But, if on the road, rotate the switch just turning the little button. This cleans the internal contacts on the switch and will get that switch working again.
Ron, Instead of regular WD40 you might want to try WD40 Silicone spray on parts you want to lube but don't want the oily on the outside. Dirt and sand will stick to regular WD40 but not to the Silicone spray.