Build a contraption with red-stone leading to a lamp that can be turned on/off via a lever as shown in the 1st picture. Flip the lever as shown in the 2nd picture. Pull back your bow as shown in the 3rd. Quickly fire the arrow into the lamp, and while the arrow is in mid-air flip the lever so that the lamps become un-powered. You will see as shown in the 4th and 5th pictures, the arrow falls off of the lamps when it should stick in them.
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Doesn't happen in 1.4.5 OR 12w49a.
You tested on Vanilla Minecraft right?
It happens in both. It was tested in Vanilla Minecraft, and I'll soon test it on 12w50a. You have to be fairly quick to reproduce it though.
Duplicate of MC-547.