The cams do wear out. They needed to be greased to keep everything sliding together properly. (the cam faces needed to be greased, as does the plunger in the lower casting) If you have the adjustable rudder castings there is a bolt on top of the upper rudder castings, and when you replace the cam, loosen that bolt and with the rudder in the locked position and slide it as far forward as possible. Non- adjustable castings? Everything might be worn so that nothing fits together tightly anymore. The rudder will have to be redrilled to get the pin in the upper casting tight into the cam. I'm not sure what you should use to refill the old hole with to redrill the rudder blade.

Try posting on the Hobie forum too.
http://www.hobiecat.com/community/index.php?sid=e6458f9057e7c7e9dc2ea6bc8e15b64b