Nano 7th Gen cancels my workout when I press the pause button for an update

Hi all,

I've recently bought a 7th gen Nano. Sometimes when running and I press the pause(lock) button to get a progress update for my run, the iPod either cancels the current workout (and doesn't record/save it) or it turns off then on. I figure that this may be because the screen unlocks when I press pause and then my pocket must press cancel. So... to stop that, I bought a leather case which makes it almost impossible to use the screen when closed, yet the problem still happens. Has anyone any thoughts or solutions? Or should I get hold of Apple and send it back?

Thanks