Pressing the button on the dispenser in the configuration shown in the attached screenshot will create an arrow which, when teleported to, shows the player’s coördinates as XYZ: NaN / NaN / NaN.

Steps to reproduce
1. Build the redstone device in the screenshot. Orientation may be important (not yet confirmed).
2. Put some arrows in the dispenser (which is facing toward the slime block, i.e. west in this configuration). The repeater’s delay should also be set to 1.
3. Press the button.
4. Type “/tp @p @e[type=Arrow,c=1]” into the chat and press enter.
5. Pressing F3 will show your player’s coördinates as “XYZ: NaN / NaN / NaN”. Running the command “/say @p” will also fail (i.e., the game appears to think the player does not exist). Relogging will fix this, but the player’s coördinates will be the same.