Tim: I think the spinlock failure may have to do with halyard tension. My halyard is a little too short. When locked with spin up, the halyard is raised off the tramp a small amount. If you kneel on it, or kick it, it will unlock. Recently, I sailed on TT's boat and it had more slack in the halyard i.e. it rested on the tramp with a couple of inches to spare. When I kicked or knelt on it, the spinlock worked fine.