Pistons do not push player properly

that`s me in a piston in an elevator

I can confirm this. It's like random. Sometimes the piston arm does push me, sometimes it does not. Using sticky pistons with a block attached is more reliable but not always possible.

this happens to me in my elevator and get me killed i hope it gets fixed

I made an elevator a long time ago, and now it doesn't work, so I guess I can confirm. Hope this gets fixed.

Made a clearer summary.

in my experience (in snapshot 13w04a), pistons do push you properly if you walk away from them
if you stand still or move in any other direction than away from them in the moment that they push you, your location will not be changed and you will be trapped behind the wooden part of the piston

I hope this gets fixed soon. In some situations, I can't find a way to have a piston push a block instead of just pushing the player, like some elevator designs that seem to work sometimes, but not others.

1.Place two pistons pointing towards each other 2 blocks apart.
2.Connect both pistons with redstone and put a lever close by pistons
3.Stand in between the pistons
4.Flip the lever and you should see this happen

MC-9861 provides a good explanation why this bug happens, therefore:
This ticket has been marked as a duplicate of MC-9861, in favor of the better description/information provided.

Since it has been moved to MC-9861 , I would suggest that everyone that has voted heree go vote there if you support this as a bug.
(Edit: clarification)