There are rivets along the front edge of the panel and directly behind the front generator slide fiberglass section. If you look underneath your coach directly under the driver's seat you'll realize that there's basically an "air dam". The speed of your coach determines how much air pressure is pushing out on that that side panel.
I used to drive in excess of 70 MPH. Heading for the San Dimas rally last year along I70 the front portion of that panel came flying up. It had even pulled the front rivots loose and tore the fiberglass above the left DS wheel well. I had the panel repaired & re-installed at a local RV / Truck body shop where they also reinforced the fiberglass mounting. They said this problem is "typical" of many motorhomes and NOT unique to WRV.
I believe the point here is a "WARNING" to check that panel amd make sure it's not coming loose in any way. And, the faster you drive the more often you should check it. If you own a mid-door model you should probably check both sides.