I also have the same problem with mine, and it's been happening since the very first day, with and without screen protector. Looks like the button works best if you touch on its upper left side and not on the middle. Looks like a desing flaw to me.
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer? | Terms of Service