Pause button does not work on ipod Mini

i just got a new refurbished ipod mini, and the pause button does not work, nor does the song pause when I pull out the headphones. Also, holding the play/pause button down does not shut it down (or put it to sleep), so I just let it go to sleep on its own, or I reset it to get it to stop playing.

Is this a hardware problem? Should I just send it back to be fixed? (I have warranty)

Thanks!