The skirt mounted to the slide has been a persistent issue for me on long trips. The portion that extends down between the axles constantly flaps as we travel. At each gas stop, I have had to retighten the lower sheet metal screw that attaches the skirt to the support bracket. While on a 7,000 miles last fall, a crack developed in the skirt near the mounting screw. So I drilled a "stop hole" at the end of the crack and replaced the flexible support from the factory with a stiffer support and added a second screw below the original.
This spring I went further with a more robust skirt support using machine screws and nylock nuts:
Hopefully this resolves the issues I have been having.