Dispensir bug

What I expected to happen wasn't that the XP from Bottle o enchanting goes out in the wrong direction when i shoot it with dispensir.
Describe what you thought should happen here

*What actually happened was all the XP what shoot in the right direction, but some create on the otherside of the dispensir.
Describe what happened here

Steps to Reproduce:
1. Put a dispensir on top of you(it have to have the hole "looking" at the ground)
2. Put a block of sandstone on the "inverse" side(the opposit side of the hole)
3. Activate the sandstone block with redstone (I had put a pulse of 2 ticks with a clock).
4. Look.

PS : Sorry, i done the best I can