Perk finally forced all devices to new versions... My nokia 520 and 521 crash alot lately 520 used to be good. My opt F^ is rocking it still but all devices seem to try to load videos to long often. My moto g is the most unstable one... The pop quiz and tv freeze often. Clearing data and reinstalling no help. The ad popup only happened to the moto g and every video played popped it up... The dang thing often never went away. I reinstalled perk and fixed it.