Had this issue recently, quite an easy fix. it's to do with the rear fog switch.
take the 2 light bulbs out inside the switch, press down on the 2 pins on the short side to release the body out of the case
pop the top cover off the chip board
You'll see a L shaped copper piece, this is the problem. you need to slide it back up into the case curve bit pointing into the spring bit, it'll fit exactly. Use some superglue to make sure it stays in place.
Put everything back together. Save yourself $50 for a used switch or $120 for a new. Buy me a beer instead.