My 10 year old Kitchnaide in the wall oven has been a very good until now. It could reach 374F on bake but would not reach 400F. I replaced the Temperature Sensor first as that job is really easy. That did not fix the problem. Next I replaced the bake element. It takes some doing. Pulling the oven out of the wall then flipping it onto its side to access the bottom. I removed both bottom pans to have full access to the bake element. It did not appear visibly damaged. However, the 10 year old bake element failed a continuity test. I replaced the element and everything is back to normal. Perhaps I could have replaced the bake element by simply entering from the back, but I wanted full access and I did not have to damage the insulation, plus I wanted to see the original element fully. Not an easy job, but I saved $$$$.