The bug

When going up to a mob with the invisibility affect, certain mobs if not all (minus zombies) do not attack the player unless the player is at their feet.

How to reproduce:

1. Spawn any other mob that is not a zombie
2. Have the invisibility effect
3. Push that mob

→  Notice how none of the mobs attack attack you

Note: This is due to how calculations work between entities and players, entity positions are at the bottom of their feet whilst the players position is at eye level, which may work as intended.