When an enderman is shot by an arrow, it can teleport to several random locations in quick succession.
This is possibly caused by the server and client teleporting it to different places.
To reproduce, go to the End in creative with a bow, and start shooting endermen. The bug is random and isn't always obvious, so keep shooting them until you notice it. It's easier to see if you're high up.
Linked issues
relates to 1
Comments 2
Why?
Enderman teleport multiple times when shot at.