my '19 NEVER failed to auto lock. When I got my '21 it started to do it like 1 out of 10 times. I have a theory it may have something to do with the fact that they removed the rear door buttons. I noticed that usually when it fails to auto lock it is because I opened the rear door and closed it last. Usually if close a front door last it will auto lock. Also, if it fails to auto lock after closing the rear door, I can open a front door, close it, and then the truck auto locks.