(Lumia 520) Why has my power button stopped working every time, within a week of downloading WP8.1

[WPCentral Question]

You may think it's just coincidence, but my mum upgraded a few weeks earlier, and says she has problems with her power button on her Lumia 520 - the same problems, it has to be caused by 8.1 Cyan update, i'm about to use NSU to downgrade mine back to 8 Black update, and see what happens

 

[Haydn Cashmore]

EDIT: it works once in every ten times or so, around the same as my mums does, it's very annoying