when you provoke an enderman as any hostile morph, it will teleport around, looking provoked,not attacking, and in my testing so far there is no way to "reset" it to normal, including switching to a passive mob or unmorphing. the only mod that affects endermen that i use is Quark, which lets them break blocks if provoked and the ceiling is too short for them to reach the player.

No idea what could it be, and I'm too lazy to investigate, sorry. 😕