[AC Question]

I have a samsung galaxy core 2 and I have noticed a problem recently. After I unlock my phone the menu button (touch lower right end part) does not work for a few seconds so I cannot access the menu. After pressing it a couple of times it works fine and I continue with my tasks but for that instant after unlocking it it wont work and I cannot figure out why. I believe it is a software problem because in any other case it works, just after the unlock it wont. I have downloaded apps to try the touch screen and it looks fine. I do weekly cache clear tune ups and phone restarts. The phone never fall from my hand.