Dry judder or wet judder?
Usually it's about the blade angle. The blade should just flip from side to side on change of direction.
This is how I'd try to fix it:
Keep the screen wet with either Fast Glass, or Rain X.
Take two of the blades & arms off,
Adjust the remaining blade until it sweeps smoothly.
Fit number 2 and repeat.
Fit number 3 and repeat.
It will be very fiddly but this should do it.
