Almost all enemy in higher level exam did have that action to attack again after killing an enemy(to make that stage more harder). My advise stop relying on clone or summon.

I don' know that, thx for this

This isn't bug. Characters in Exam are modified. In other words, they are stronger than their normal versions.

That's the evolved form (3 star) for you, had him in the chinese server he's broken as fck and his standard attack turns into 4-5 hit and low float. Qnce he reaches 4 star his appearance adds on a ninetail skeleton on top, mystery: tail best gun volley, and standard hits 3 targets at once.