I have this KitchenAid double wall oven that the lower bake element failed on. I replaced it and it has failed again after 2 weeks and just a few uses. Wondering if it's a bad part that just failed or if I need to be looking for another cause of failure, it's quite a project to replace. I did notice the metal shield under the element was very warped & heat discolored, don't know if that's normal?