Slowly push the door closed and feel to see if it moves up or down as the latch grabs it. If it does then the hinges are out of adjustment and he is using the latch to compensate for it which will wear out the hinges, the latch and on some cars like E-bodies cause the door handles to break.

The doors should be fully loaded and the hinges adjusted before the latch pins are installed. That way the latch only latches the door and doesn't force the door into position because of mis-adjusted hinges.

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