first i think you mean Manda not Madara ^^ but to your problem: the message "System error" while pressing a mystery only comes if your ninja is already dead but you just havent seen the animation yet

ill try it out with the new reset but i just think you are still to weak / dont have enough def/res/hp yet

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i just tested it and for me it works as it did before
well manda has bloodthirst which means it attacks again if it kills something (even clones)

Tested it myself to confirm that Ninja Exam 85 is not bugged.

As Syldor stated, Manda has bloodthirst, be wary of that.

If you're having performance issues. Try playing it on the browser version to see if it improves.
If you have any additional questions, feel free to PM me.