Endermen do a weird half-teleport any time they take damage, where they warp somewhere for a microsecond, and then instantly return back to the same location where they took damage at.
How to reproduce:
Make the enderman take damage by any means (other than water): punching, cactuses, magma block, campfire, iron golems, falling anvil, fall damage, etc.
Best tested in night time, as they don't do the random teleportation they do at daytime.
MC-101700 Missing server-side check in enderman teleport