I too experience this, or when I press it and it does the animation on my screen and then I'll press cast ninjutsu button and it doesn't cast, while I continue my combo I will have the rabbit symbol in my cross hot bar because I continued my rotation. It would be nice if you didn't make it so the rabbit comes up if you continued your combo after your mudra chant is complete. Like after Jin- Chi -Ten if you pressed ninjutsu and it didnt cast. and you continue with spinning edge it wouldn't make the ninjutsu a rabbit.