So this happened to me a few years back and the dealership opened it up for us while it was in for other issues. WD40ed it up and problem solved. Maintained it with regular WD40 lubes and then moved to the pacific nw from the high desert of MT. Solution no longer works. Maybe it just needs more...
So my exterior rear door handle fell off the other day in my hand....... Didn't know I was such a beast :) Anywho, seems like a simple fix, I believe the bolt for the 'cap' was rattled loose. I removed the door panel and punctured the round white sticker that covers the hole which is in line...