Work out which direction they are juddering in.

Flip up wiper arm, grab head assembly firmly in both hands and twist it against the resistance of the arm, so it's more inclined to "flip" in that direction. The thin tin of the head assembly is quite easy to "tweak".

Works for me.

I think TC means (could be wrong in which case sorry for poking me oar in TC..;) that over time your wipers may have developed a twist one way, and you are simply correcting that and putting them back to upright.

Linkage might also need a bit of lubrication and do check its securely fixed, assuming you can get to it, having helped my son replace a Toledo heater matrix (the job from hell, never again) i'm none too sure on access.

Once this is fixed i have a useful tip which helps to make wiper blades last a long time and helps stops the judders....your blades usually park leaning one way, when you leave the car for several hours or overnight simply flip the blades the other way especially useful in long dry spells...apart from keeping them and the screen clean, and preferably not washed with a wax car wash, thats it.