Are you using a protective cover or case that has little magnets? If you are, that's the problem. Remove your Tab out of the case and see if this resolves your issue. My Tab 3 starting to lock up and freeze as well as being unable to swipe the locked screen. I diidn't realise the little magnets in my case were the problem. I'm planning to cut out the magnets coz I don't wanna purchase a new case. Good luck!