Just a few comments about this problem.
First, the question about the intermittent. It is controlled by the wiper relay.
As for the wiper adjustment, the usual problem is the right wiper hitting the A pillar. It can be adjustment or worn parts. If the arm and links are worn, the momentum of the wiper blade and arm will make it travel further then it should. This usually only happens when the windshield is wet, but not when it is dry. I found a fix years ago. I just removed the right wiper arm and blade. You only loose about 2 or 3 inches of wiped area on the right side. Not enough to make the wife upset. I latter replaced the wiper assembly with one from a later model with less miles and not worn out but never put the right blade back on. After all, a lot of Mercedes only have one wiper. It also cuts the cost of wiper replacement in half. Mine has been this way for about 10 years. Never failed an inspection. Less wiper noise. This is a win, win, win, win fix.

Ok, let me have it, I'm ready

Paul

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84 500 SEL (307,xxx miles)