It seems the progression is first worn hinge pins, causing the door to sag. This, in turn, causes the little latch "fork" thing that locks when closed, to often strike (and wear) the top of the door jam lug. Also, I've observed that the actual shaft and hole for the latch "fork" thingie wears, compounding the problem. So it isn't just one thing wearing out, it's a combination of hinge pins and latch mechanism (left ones wear out, likely the right one is still like new). The left door on my '80has this same problem. I fixed the pins, but now am dealing with a worn latch.