Anyone else have a problem with their Nexus. I've only had mine a week and I've noticed that sometimes when the screen goes back to the lock and you have to unlock by swipping, mine swipes, unlocks then within a second locks again - once it does that the only way to unlock the tablet is to turn it off and turn it back on again. Firstly, does that make sense and if it does does anyone know if I'm doing something wrong or if the tablet is faulty.