I had the same issue. I ended up ordering/installing a new roller sunshade. Part 51469178931 ($614.39 + shipping). It's an easy install. For me it was easier than changing out the cabin filter. :C)
However, I was messing with the old broken one..just curious if I could diagnosis the issue. The motor seemed fine. The rails looked good and no broken pieces. There is a site that claims they have a part that will fix it. But I looked at that and didn't see that as an issue. Mine just got stuck a few inches from top on the way down. Anyhow, I sprayed WD-40 everywhere possible. Still same problem. I even removed the screws by the motor that seems to have some adjustments, albeit small, to move it & adjust motor position side to side. That didn't help either. But, then I noticed another screw, that didn't seem to hold the motor in place. Picture below. I turned it to loosen with about 6-8 rotations. Then I tested the sunshade and boom. It went down! I'm not sure if that is some sort of torque adjustment or I just got lucky with the combination of doing all of the other troubleshooting tests. Since I ordered and had the new sunshade already, and with a 25% restock fee, I went ahead and replaced it anyway. So now I have 2 working sunshades. You may want to give that a shot.
Steps to install roller sunshade:
1. Remove 3 screws in trunk
2. Fold seats down (hopefully you have that option, if not I think seats are easy to remove)
3. Remove 5 plastic screws with plastic prying tool, 2 of these are hidden behind 2 (left/right) seat pieces. Just pull those up and out to remove the seat pieces.
4. Remove 2 ABS (airbag) clips and then 2 screws. ABS clips were hardest thing. I had to use Very thin screwdriver and hammer. But then they just pop off. None of my pry tools were thin enough.
5. Lift rear deck/parcel up..jigging it. And then go ahead a just unclip the speaker wires.
6. Take sunshade out from bottom. Just angle it and bend the parcel/deck to wiggle it out.
