Your drivers door hinge may have some wear in it, allowing some up and down motion. My 88 drivers door is that way. Because of the wear, the door actually wants to strike low, but the wedge and door striker "jump" it up into position just as it hits them. My wedge was actually broken and I replaced it. The wear in the hinge caused the new wedge to break within a few closures. Now it is just the same as before. I bought a used hinge set off of another spider, and one of these hinges has wear, one does not. I am assuming that the one without the wear is from the passengers side. I am getting ready to install that hinge in place of my drivers hinge, on the assumption that the passengers side gets less use than the drivers side. The hinges appear interchangeable.
The 2 leaves on an Alfa spider door hinge are cast steel, and the hinge pin is actually a split roll pin. It seems to me that the split in the roll pin is scraping away at one or both of the leaves as the door swings back and forth. If replacing the hinge on my car corrects the problem, I am going to see if a machine shop can press out the roll pins, ream the holes, and install a solid steel pin with an oil grove so that the remachined hinges can be lubricated in the future. I will add a post when I change out the used hinge and let you know if it corrected my problem.
Robert