Originally Posted by r carl
The problem is most likely the angle that the blade is contacting the windshield. The wiper blade should contact the windshield at a 90 degree angle. If the windshield wiper arm has twisted slightly over time the windshield wipers will chatter. A little work adjusting the wiper arm should help. In the past I have used an adjustable wrench on the flat part of the wiper arm and twisted the arm slightly to get the wiper to contact the windshield correctly.
I suspect you are correct. Applying the Rejex to our windshield seems to have made the problem worse instead of better, which I never thought possible. Having exhausted the potential of both surface applications and blade brands, we now have to turn to twisting. Fortunately there are pointers for that on Sprinter Forum.