The Day/Night shades can be adjusted by loosening the screw that holds the string at the bottom and giving the string a little slack. With time and usage they will naturally loosen and have to be tightened, which may be what has occurred, someone has tightened them really tight.
I had a problem sliding my driver window and more due to lack of anything else on hand used baby powder in track. Free'd it up for a while!
Tim & Mary Discovery 40X. Chevy Tahoe. RVM32
"I've been lost now, days uncounted..."GFR"