When I tried some tactical stuff with snowballs and eggs in minecraft 1.9, I found out that if you are standing too close to mobs (between one and two blocks distance) snowballs and eggs won't hit them. It seems that the snowball/egg disappears just before it should hit the mob.
This problem also exists in the three pre-release versions of minecraft 1.9.1!
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Most likely, else, cannot reproduce
This issue duplicates MC-88491