The end of the cylinder has a little pin sticking out. The pin engages the lever that moves the locking bolt. My guess is the pin may be broken off. Take it apart. With a small hammer use a sharpened screwdriver to penetrate the freeze plug cap thing on the bottom and pry it out. It's real soft metal. You'll be able to see what's going on then. There is also a pin that the lever rotates on. If that pin was broken it might do the same thing as yours is doing. Not sure. The cylinders are available at Memory Lane or from Wes Pinchot near Chicago, a classic bike guy. Gary