Hello Ale.
To work properly, the wiper blade rubbers need to be at 90deg to the windscreen so that they will "feather" correctly in both directions. My Plus 4 wipers only worked in one direction when I first tried them and juddered badly on the return.
To get them working, I took the blades off the arms (as you would to replace them) and then very carefully bent the arms until the tips that hold the blades were flat/parallel to the screen. I used grips to hold the arms at the very tips (so any marks don't show as this area is within the wiper blade when it is refitted) and with thin card to further protect the arms. With all three blades refitted to the arms, I wet the screen a little and tried them, making small adjustments as necessary to get the best performance.
I've also seen a number of cars with the wiper arms bent into a curve, which I think owners do to increase the spring pressure on the blade. I haven't resorted to this yet but hopefully other owners will also share their experience/views to guide you.
I've used the above technique many times over the years to improve wiper performance on a selection of cars so hopefully it should work for you on the Aero too... good luck.
