Seems like I'm in this same boat with my 2016.

The rear window has always been slow in the winter, but over the past year or so it's been somewhat sluggish even in the summer. This morning though (-17ºC here) I accidentally hit the down button while driving and it wouldn't go back up. Tried from inside and outside, no luck. The only way I could get it to roll back up was pull the button on the console, it moved an inch or so... wait 2-3 minutes, pull the button again... another inch or so... wait...

I'm guessing the grease on the mechanism is frozen, or at the very least thickened up, to a point that prevents it from moving correctly. I'll have to get it into my shop garage as soon as possible and pull the rear panel, clean up the mechanism, maybe re-grease it with something very light and temperature resistant?