I have self learned that there is a factory defect in hydraulic chamber in hair cutting chair lift. This product is manufactured in #turkey and its a rubber or fiber or plastic washer that deteriorate over time that keeps the valve getting hammered by the lift shaft. It breaks in to small pieces and clogged the oil pump piston release valve. I replaced it with a plastic washer which I believe will stand the hammering for a long period. hopefully will not come back for repair again. :)