I just bought a Sunbeam breadmaker, the loaf rises to the top of the pan very niclely, with a slight curved top. When the bread starts to bake the top of the loaf sinks down about an inch and caves in a little. What causes this? My kitchen is quite cool, old house. What temperature should the room actually be to bring ingredients up to room temp? In the manual it said 75 - 85 degrees . Is that correct?