Hi David, As you say, there could be the possibility of a slight misalignment of the door latch, and the door latch striker? The door itself may have slightly settled over time, and the striker in effect now may be a bit high.
This can sometimes be seen if observing very carefully when the door slams, and latches, if the door appears to be raising at its closing point ever so slightly. Perhaps the use of masking tape will show this more precisely. Also look for any unusual rubbing at the latch striker.
Also make sure that the doors are even, and in line with the next door, or quarter panel behind it. If not, the striker needs to be adjusted inwards a bit. (To do any striker adjustments, it is helpful to mask around the striker in its original position with masking tape, this way you can always return to the original position if need be.)
I would lube all door hinges with oil, and a light coat of grease on the little plastic thingy by the hinges, which someone else has mentioned, clean, and then treat all door weatherstrips with Amour All, and also check all rubber hood stop bumpers for proper adjustment for height, making sure that the hood is in proper height alignment with the fenders (easy to do), and also give them a light coat with some grease.
The only other thing I can think of looking into, and checking for rattles/noises, would be the sideview mirror. Also, try this experiment, but with the window fully lowered. Hope this helps you, Mark