I have a Whitfield Optima 2. It shuts down in about 10 minutes. I've tried removing the photo eye and cleaning it and the lens and it still shuts down, but if I leave it (the photo eye) out and shine a light on it the stove stays lit. There are no obstructions when I re-install it. Will a new photo eye work better? Or what else do I need to check? I've tried to remove the lens on the stove to clean the underside, but am unable to loosen the nuts. Any help is greatly appreciated.