I think you will need to look at a schematic or remove the lower plate that covers the interior and look at the mechanism. If it is a gear to gear arm lift then it should be easy to spot. If a electronic lift then you will have to study it. If gear to gear then some kind of pressure band must be used. That may be worn. It would look like a rubber band but small that puts pressure on one gear to mate with the other when the button is pushed. Or a swingarm might be used. You must find a schematic.