You guys that are having door lock issues - when you try to lock it with the key fob, does the vehicle do all the "other" things that would make it think it's locked? Like turn off lights, honk horn, or whatever?
I'm wondering if it's a signal problem, or a physical/electrical problem. My daughter's Charger had an intermittent door lock issue, and it turned out to be a faulty relay on the BCM board (had to replace the whole BCM because of it). In that case, you could physically hear the relay failing (it was a fairly loud click under the dash when pressing the door lock button). Even if your problem isn't due to a faulty relay, I'm wondering if inadequate voltage to the relay would be causing it. Or is it really a software glitch, and the truck isn't even trying to lock.