This isnt patched ...
I did it a different way though (on PS3)
1. *Best to do this going DOWN*
2. Keep jumping but when you jump up press Start and Triangle really quickly.
3. This may take a few tries but I've done it and it is REALLY boring ... but if you fall behind the elevator, move to the other corner (opposite of the Double Tap machine) you can see the zombies move their hands through the wood so you can knife (preferably Ballistic Knife or Bowie Knife) them or shoot them.
NOTE : If you are the host, and you are trying this way ... this will make the game lag. If you have sh** connection right from the start and this happens with the host ... you WILL PROBABLY timeout.
Happy Glitching