I had the same issue when I first took delivery of my Dutch Star, shade would bounce and rattle. I installed a strip of 3M Dual Lock on the back side of each end of the bottom bar of the shade and then a strip on each side of the vertical window frame. With some downward pressure on the shade, I lock the Dual Lock pieces together which holds the shade in a taught position and stops the bouncing and movement. I have rolled the shade over in the photo to show the backside of the bottom of the shade with one side of the Dual Lock installed. The other locking component is on the window frame.
Some might call this product velcro (hook & loop) but it's not. It is a far stronger product with significantly more holding strength than velcro. It's also quite expensive but you will find it has multiple uses around your motorhome. Here's a link to this product on Amazon:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
This solution has worked very well for me, no more bouncing and rattling.
Hope this helps.