We are on our third microwave/convection oven Model #405.75153310, and if you reheat a casserole or use the microwave for an extended period of time, the glass fogs over. This happens between the glass, not on the inside or outside. Is this a problem that needs to be a recall or what. We purchased our first one 11-18-14. We then called customer service and they told us to return it to our Sears store. All three have done the same. What should we do now. Is it safe?