The auto wipers on the GTA have been playing up - stopping part-way through the cycle in intermittent mode and juddering badly on all cycles - I have Bosch blades so it wasn't them. It seemed to be worse when the screen was only slightly wet. The screen is new and has "Rain-X" applied.
I have similar problems with my JTD when purchased that was traced to the wiper ECU. So yesterday I decided to investigate. The ECU is located under the windscreen scuttle toward the passenger side so only that side needs to be removed. A word of warning, be gentle when removing the scuttle, there are several plastic pins close to the windscreen locating the panel that need to be "popped". (I levered GENTLY against the screen using one of the plastic trim removal tools bought off ebay, but consider protecting the windscreen) and don't forget the screw by the bonnet hinge!
There is also a sensor attached to the ECU, (believed to be part of the climate control) that doesn't affect the wipers and can be left alone. I unbolted the bracket and removed both parts. The first thing I noticed was the stiffness of the connection plug to remove.
It was obvious that the connection pins of the ECU were badly corroded; these were cleaned using a fibreglass "brush" and sprayed using contact cleaner. The plug was cleaned and a wipe of silicone grease applied and all parts re-installed and the scuttle replaced.
The result? The wipers work correctly, there is no juddering or stopping part-way.
I can only conclude that if the wiper ECU detects an excessive resistance the wipers judder or stop, in my case this could be due to an increase in electrical resistance compounded by the dry-ish screen.
For me it was a free fix and didn't require pulling the wiper motor apart. It has to be worth a try