Endemic in the darn things. I have 3 sets of brand new 65/66 deluxe panels in stock, two still in the plastic and in the box that are warped. One other set new but shop worn...same thing. I tried putting them on a rack with weight opposing the bend in the heat. It came out but came right back. Maybe thats why the vast majority of them on cars (non shelbys that I deal with) have a few screws holding them on. A friend just installed brand new panels on a build. He used screws. Another friend with an E car, Screws in his door panels. How the suppliers can't sort this issue out is beyond me.