Just a thought, and relevant info to add here.
The contact wheel inside the gearbox is covered with grease, and caused intermittent contact, which causes the stutter. I cleaned mine after reading about this here 3 years ago, and its been fine ever since.
Remove wiper motor assembly, and take cover off of gear housing. You will see a wheel that is covered in grease- wipe the surface clean and reassemble. Pretty easy free fix. You might spend some time putzing to make sure wiper linkage is aligned if you don't mark it before you start.
Remove these screws using a T20 torx bit.
Pry the cover off. It will sound like stuff is cracking and breaking but it is only the adhesive that holds the case together.
Wipe contacts and contact surface clean and reassemble.