When a VillagerGolem attacks a hostile mob (In this case, an endermite), after the VillagerGolem kills 1-3 more mobs, the A.I of the VillagerGolem goes into a "Zoned-Out" mode for 1-4 seconds, then resumes to kill 1-3 more mobs, and then "Zone-Out" again, etc.
This issue duplicates MC-73724