(This article needs a lot of editing.) In a book by Freeman Dyson, who worked for the British Bomber Command during WWII, he says that the escape hatch on a Lancaster bomber was too small for the average man with a parachute, and this was never fixed.
I read a book “The Thousand Plane Raid”, and in it I recall there were men bailing out of the plane, one had to sit on the floor, and the next person had to nearly sit on his shoulders to get out. It was apparently a very small, awkwardly placed hatch. I have heard there were four escape hatches, but they must have been difficult to get out of.