Chaos Awakens version: 1.16.5 - 0.9.0.3
Tested entities: Robo Warrior, Robo Sniper, Ent, Hercules Beetle

Description: I used the Chaos Awakens mod with the Mob Battles mod. And most (or maybe all) hostile mobs does not seem to fight back.
I sent a group of zombies to attack the tested entities and it seems like they would only kill one of the zombies, then it would not fight the others anymore.
A solution to this can be adding the HurtByTargetGoal to the entities' AI code.

Here is a recorded video of the issue. (I used Streamable because the video file size is too large)