[sick472]

If your doors are not sagging and you determine the problem is at the latch betweeen the door jam and door...the post mounted in the cab can be adjusted. It sounds like the weather stripping is keeping the door from "stopping" long enough for the mechanisms to catch or the mechanism has slowed down. I would try some lube in the parts in the door first to speed the "cacth" back up.

If the door, when fully closed, is below flush with the cab...try shifting the post outward just a little. This procedure can be a trial and error exersise. I use masking or elec tape put on the cab's door jamb to show where the post was so that I have reference when moving it or incase it has to go back where it originated.