I have not had this problem with my Rampages. You you really open the boot up to put your feet in? Or do you take the liners out alot? My friends langes did this because he took the lines out alot and putting them back in puts pressure on the back.
Take the liners out sometime when I want to dry them but the forces of doing that are nowhere near the forces put on them when skiing. They broke dropping a pretty big cliff