Have you tried cleaning the leaf switch? I normally just use an index card or a white business card. Place it between the leaves and press on it while moving the card back and forth until it comes out clean. If it is really gunked up, a drop of 90% isopropyl alcohol on both sides, then press and move the card.
If you can find one, there used to be burnishing tools you can use. Do not ever use any kind of sandpaper as this will remove the gold plating on the contacts.
ken