My windshield wiper blades were replaced by BMW when I brought my car in for maintenance a few weeks ago. Ever since, they behave weird in the rain. They don't exactly chatter, they just "bounce" when they change directions. So, when they both come back down to their resting position, they bounce/wiggle in place before coming back up. When they turn around to come back down after the upwards wipe, they bounce at the turnaround. In the middle of the wipe, they're just fine.

I was planning to stop by the dealership for another question so I brought it up with them then, and the guy started cleaning my windshield and said it felt weird, like the glass was "grabby." I think it was treated with some sort of water repelling sealant before I bought it (got it used a year ago, it only had 2k miles on it though) because it's always beaded and repelled water in rain really well. I have no idea what sealant may have been used though. Anyways, he cleaned it with a couple different cleaners, cleaned the blades, dried it, and had me run the wipers with the fluid. They didn't do the bouncy thing, so I was satisfied and left. Less than a minute of driving in the rain after leaving the dealership they were at it again. I tried running the washer fluid while driving in the rain and that made it stop briefly, but it picked back up again. It seems the washer fluid adds enough lubricant between the blades and the windshield to counteract my "grabby" windshield.

The dealership guy's thought was the new blades are so nice and fresh and sharp, they're being affected by the surface of the glass having this coating or buildup or whatever on it, while the old ones weren't as sharp, so they weren't grabbed by the glass. Does this sound like a logical conclusion as to why the issue only started AFTER getting new blades?

In any case, it seems apparent that I need to do some heavy duty cleaning on the windshield to get this sealant or whatever buildup I have on there off. I'm open to the idea of buying a new product, however, I do have Klasse AIO, I could get IPA from the grocery store easily and cheaply, and I have glass cleaner/polisher designed for a glass stove top which I bought to remove water spots from my bathroom mirror (and it worked very well). Even though it's not designed for glass you look through, is it OK to use on my windshield? I want to treat my windshield right, so if there's any doubt that the stuff could mess it up or isn't ideal I won't do it. I have a couple clay bars, I could use one for this if it requires that kind of intensity (though I was obviously planning to save them for the paint). I also have the cobra waffle wave glass towel (and Invisible Glass, but I obviously need more cleaning power than that, since it's what the windshield was cleaned with right before the new wipers were put on).

In case it's applicable, I use P21S Windshield Wash Booster, maybe 3/4 of a cap full when filling the washer fluid tank.

So, my questions are, does it sound like the sharp fresh new wiper blades are reacting more to my windshield just because they're so sharp and fresh? Does it sound like the issue is some old sealant or buildup on the glass? And can I use products I already own to clean it off?