Is Amination function bugged?

When I use the action "Amination: unit do attack amination", the units just "freeze" in the attack position instead of attacking continuously. (Very much like they want to attack a powerful wizard but were frozen by him before they can swing their arms.)

Can anyone tell me why this happens? Is this a bug? How can I solve it? I found many other custom games have amination but I can't figure out how they do it.

Thanks!