OK guys got the above machine and have a question concerning the knee clamp. pushing to the left clamps the knee in place, and pushing to the right unclamps the knee. When I push the lever to the left from the off position I hit a hard spot where it wants to stop but if I push further it kinda loosens up and pushes further. So the lever feels like it hits the lock spot but after that if you keep pushing it gets looser and keep going. There is no permanent stop like in the x and y axis locks. Is this normal and anything to worry about or think about repairing?