Wiper judder driving me insane!

Guys, I really need your help. I started getting juddering wipers on my 2012 S3 a while back so I took it to the dealers. They kinda said its not covered by warranty but agreed to replace the wipers. Anyway a few hundred miles later and it started again. I thought it might be something to do with a rain repelling product I used (can't remember which one) so I used fairy washing up liquid, autoglym glass polish then several cleans with fast glass. Still the same so I eventually decided to repeat the process and replace the wipers with some brand new Bosch twin blades. Guess what, a few days later and it's back!!! It actually making me think about getting rid of the car!! Does anyone else get this or more importantly, resolved it? Can the pressure of the wiper arms be charged?

Any help would be welcome. Admittedly not a huge problem compared to some but very very frustrating!!

Cheers, Chris.

Cheers guys. I only ever applied the repellant once so thought I'd have gotten rid if it with extensive glass polishing. Maybe not.

I'll try and twist the arm slightly and see if that works. The arms have never been removed as far as I know.

Even with these new blades the bottom of the drivers side blade rattles about the screen as if its hardly touching it.

PITA