With the phone off, hold power + volume up + home for a few seconds until you see "Recovery booting" in the top left hand corner in blue letters. Then use volume up and down to navigate recovery to get to wipe cache partition. Use power to select the options
Sorry for the late reply. Sounds like it might be a bug with the app then, but I haven't had problems with it. I don't think a factory reset is something you'd want to try just to fix the app though