One of my keys had completely stopped working and I had basically written it off after changing the batteries had no effect. A month later I decide to do a little searching and ran accross this nearly 10-year old post. Bending the metal strip worked like a charm! Key is perfect now. Don't know if you're still around the forum, but thanks SoCalC240!!!Good luck. To clarify, when you take the battery out, you'll see that the thin metal strip that holds it in place is basically straight. What you want to do is bend it slightly so it forms a very light U shape.
This puts the center of the strip in better contact with the center of the battery.
This is a problem that happens with all the keys, the old ones and the replacement ones.
(That being said, the keys seem to have other problems sometimes, too. So there is no guarantee this will fix it - but it only takes a couple minutes and is worth a try!)