I have two FL9s and neither has a diaphragm attached to the rear door if that is what you are asking about, however you should direct your question to Scott Mann of Sunset Models / Third Rail Division. He is a good guy and he even sent me a UPS return label for one of my FL9s that is not properly receiving the TMCC signal. Lionel and MTH don't do that unless you really complain about their product that did not run right out of the box.
Ed G. (Along The New Haven Line of Metro-North and Amtrak in New York State)