My 5th Element lost it's rebound dampening after a few hundered miles. While I had the shock off to put on my warranty-replacement-upgrade DHX Air I tried something with the 5th...
I let out all of the air from the pedaling platform chamber. Then let out most of the air from the main chamber. Then I was able to compress the shock about half way when i pressed it vertically on a work bench. I don't remember which end I had up, but I heard a "CLICK" from inside, and suddenly the rebound dampening worked like new.
Don't know how long the rebound would continue to work. But it might be a solution for some while you wait for a replacement.
-B