there are sometimes cases of mobs attacking me and I cannot see them, my friend was on the world at the time and could see the zombie and killed it, I saw the loot drop and the particles but not the mob, also in another case a zombie villager was not moving whatsoever and still attacking me, I thought I was safe because it was far enough away but that was the visual glitch. on a different occasion, 4 or 5 villagers were missing from a house we had them in, I could see three of them and I thought the others had escaped but my friend saw the missing ones