The commandblock teleports the player not on right z coord what was given to the tp command, it adds 1 to the z coord (if you enter z: 100, it will tp you to z: 101)

What I expected to happen was...:
That it would tp me to the right z coord.

What actually happened was...:
It tp'd me to the right x & y coord, but not the right z coord.

Steps to Reproduce:
1. Open Minecraft 13w09a and go to Singleplayer and open/make a creative world (prefer superflat classic).
2. Teleport yourself to x: 0, y: 10, z: 0; with /tp @p 0 10 0.
3. Do /give @p 137 in the chat and place the commandblock down on the ground.
4. Open the commandblock and enter in the line: /tp @p 10 10 10; and click on "Done".
5. Power the commandblock with something like a button/lever/torch
6. You will not be tp'd to x:10, z:10, but something different like: x: 11, x: 9 or z: 11 or z:9 (it can all happen, I'm not sure if it always does +1 to the z coord, it's just that it doesn't works properly)

Note
1: If you use a locator in a commandblock like @p[10,10,10], the 10 10 10 also doesn't works always. It's buggy.
2: This bug was there longer then since 13w09a. I don't remember when it started, so I just chose 13w09a.

Attachment
In the attachment you can see I entered as coords: 256,59,-1450; and it tp'd me to 256,59,-1449