"Focal Dystonia"
Essentially, this is a sensory problem. The nerves in the face cannot control the muscles of the embouchure anymore in certain areas of register. This tends to be degenerative.
From a good friend and formaer student of Mr. Decks, I have heard this is what he has. His chops basically won't respond in certain registers. As far as this being equipment related, this has not been truly established.
The best way to find out is to track down one of Mr. Deck's last students and ask them. Get a lesson while you're at it. Anyone who did study with Warren Deck seriously knows how to play.
For more information, simply "google" Focal Dystonia with an emphasis on Embouchure Focal Dystonia and you'll find plenty of information.