Endermen teleporting insanely when it rains

Ever since 1.9pre1 when Endermen teleported out of water if they fell in it, a weird and humorous bug has existed where if an Enderman is caught in rain, it will uncontrollably and crazily teleport all over and can sometimes even teleport right in front of the player. Another glitch involved with this is that if it teleports on a slab (Not upside down) It will stop taking damage and thus stop teleporting.

Causing this bug is easy.

1. Spawn lots of Endermen.

2. Get ready and watch carefully, because it'll happen fast.

3. Toggle the rain and watch the Endermen go into a teleporting frenzy!