maby, but i need to test this
i made a server in 14w06b with a map with all of this ingrediants and run it, after that me and my friend placed a command block with this command "/summon Item ~ ~1 ~ {Age:-32768,PickupDelay:32767} then i palced a button on it and pressed it and then everything died.
i attching a video in showing this bug (Its in Hebrew).
http://youtu.be/S_2kNl-Z-Vk?t=1m3s
some get removed and some get killed, like cats not killed, slimes removed and player get killed
yes that was command block near it with this command:
/kill @e[type=!Player,type=!Ozelot]
and it killed anything but the cats.