The major issue is that if you open the door when frozen, it won't shut again until you warm up the car or saturate the rear locking mechanism with a de-icing compound, and then spray with grease.
The lock mechanism at the rear of the sliding door will bind in cold weather. If you spray grease into the locking mechanism regularly it will minimize problems. Use WD40 or other light oil to loosen up the mechanism the first time. Within a couple of days, spray in grease to saturate the area and maintain a longer fix. Repeat weekly during cold weather.