Ender dragon not leaving egg after dying

I have killed the dragon 3 times but when i killed it for the 3rd time it didn't leave the egg (ender dragon egg)

I have killed the dragon 3 times and i have respawned it 2 times using the egg but the third time it didn't give me an egg after killing it. i don't know if its limited only to my seed but if it is then my seed is -1401743908