I had this problem with my right front door last year. My solution is to not use that door since I rarely haul people around anyway.
This year though, I had another problem similar to this. My left rear door can't lock itself without me pushing on the lock. And that had happened at any temperature so frozen water could not have been the cause. I sprayed some Tri-Flow (it's basically WD-40 with Teflon) at the locking mechanism and after a few days, the problem went away. It has not had the same problem for a few weeks now. *knock on wood*
