Dave. I would use a glass cleaner on the screen, more than once. But test before applying Rain X. The flat screen of Morgans prevents water droplets migrating upwards, so Rain X doesn't work in the same way as on a conventional screen.
I would be inclined to remove the arms and blades, then try each one in turn. It could be that one is causing the judder. If you can isolate the cause it will be easier to find a solution. I would also apply rain X to the blades. If the judder is only one way, it may improve if the blades are adjusted to give more of a trailing angle in that direction.
Judder is usually a combination of blade angle, pressure and friction with the screen surface and it can be infuriating, so good luck.
