I'm rebuilding my vnt 15 turbo and all is well until I tighten the control ring plate. When loose the control ring moves freely and the vanes move as they are supposed to. When I tighten the three star screws on the control ring plate it tightens down on the vanes then won't move. I have the spacers in exactly as I took them out. The turbo casing is bare metal and thoroughly clean. What am I doing wrong?