All of the windows that open on our Airstream tilt out from the bottom. Since new, I've had to go outside with a plastic knife and help the window start pulling away from the seal strip on the trailer. I've tried graphite spray and just cleaning the seal strip and the window trying to eliminate any stickiness, but nothing helps. It would be nice for one person to be able to open the windows from the inside. I'm out of ideas. Anyone?