Random Unlock Screen Wont Show Problem...Anyone Else?

Hi all,

I have had my Z10 a week now and its only happened twice at really random times when the phone has been locked I press the top power button to bring up the swipe screen but nothing comes up screen stays off and the notifications stop flashing......I then hold down the power button and it shows me the timer, I press the lock button on the screen and it then comes up for me to unlock. Anyone else had this? not quite sure if its software or hardware related?

My phone is stock OS 10.1.0.

Thanks