We purchased four new Blodgett DFG-100-XCEL convection ovens back in 2006. From day one we have had problems. Our cooks place food in them, set the timers, and the cooking process starts. They come back later and the oven is cold. Opening the door and closing results in the units relighting. This leads me to belive the ignition control has been locked out for a flame problem. I tried new burner packages, new ignition contols, and new temperature controls, but one or more of the ovens is always out of service. I take care of 126 pieces of equipment in our kitchen; this is the only one I cannot resolve (and I believe Blodgett is a fine product name). Any ideas, PLEASE?