I've not experienced your issue, so I'm sorry I don't have a good answer. However, have you removed your screens to gain access to the window arms? Mine seem easily accessible (and presumably an easy fix) with the screens out, although I don't know why they aren't staying in for you.
If you're already headed to the dealer, I'd have them take a look and take advantage of that 2-year warranty. And keep us posted on what transpires for us fellow frameless-window owners. Thanks!
2014 White Hawk 30DSQB Summit Edition
2007 Ford Expedition EL 4X4 5.4L gas with 3.73 rear