The shut-off diaphragm - is this somethign that should be changed on a schedule. Perhaps checked often - but even changed out - to prevent possible breakage and ultimate run-away. As I understand it - the STOP lever in linked to "shut-off" IP. Why would'nt it be connected if shut off diaphragm leaks. OR are we talking about work having been done on IP (overhaul, etc) abd STOP being disconnected? If no work is done on IP - then STOP should generally always work? Is this correct? Thanks