Siri's bugs?

hi, I am using iPhone 4S with iOS6. (i bought it several days ago) I find that Siri has some problems. It can easily get stuck and go into the stage "Sorry, I don't understand please repeat..." after giving several commands to it. At this state, no matter how simple and how clear I am speaking it just always returns with that "Sorry, I don't undestand....." until I reboot my iPhone

Is it the bug or the internal hardware problem of my iPhone?