I'm not sure about an older Open Road, but my 2018 works the same as you describe except that my screen will shut with the window slid open. Or they will slide at the same time and stay together if I slide them together.
Yours may be just stuck together as mine does at times, but they are easy to slide separately. Probably just need to work with it to get the screen unstuck from the window. My other sliding windows work the same and the one behind the sofa was really stuck together when I bought it, but I managed to unstick them with a little encouragement.
Wade & Debby Griffin
2018 Tiffin Allegro Open Road 32SA, Ford F53 24K Chassis
2012 Jeep Liberty