I still don't understand.

But I do believe you know what you mean, its just hard to explain. You may have to draw us a diagram or something.
So is it possible that the air cell is drawing down so much that it looks like they are past it, when in reality, they are actually hitting the air cell? If the membrane is pulling away from the shell, it would pretty much have to be "part of" the air cell. I can't imagine how the inner membrane could pull away from the inner shell without starting from the air cell.