When we set oven to bake it preheats and works for ten or 15 minutes then the lock comes on and shuts the oven off. It keeps doing this over and over. We replaced the oven switch last week and the oven worked for a week. Tonight we tried to bake a roast and it kept locking over and over and turned the oven off each time. I have read page 47 of the manual. I press the two buttons at the same time and it looks like it works but then when I reset the temprature it gets to the right place and the lock comes on and shuts the oven off again. It is getting awful frustrating. Hope someone can help me. Maybe I have to replace the oven switch again?