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[Mr_Roboto]

There is a nylon bushing on the door "pegs" that the latch goes around. Those wear out once the doors start sagging from the weight being held by the pegs. You should be able to get the nylon bushings from the HELP! section of your auto parts store.

Also make sure that your doors are adjusted properly, and rebuild your door hinges if they are very loose. The door must close with the latch directly level with the peg. If your door "lifts up" when you close it, and "drops" when you open it, then the door is not adjusted properly.