So when I get back in my car after being at the gym for 2 hours, it will say for example "3 notification" and then I click sentry mode on the top right and then viewer and then there's absolutely no footage..I'm surrounded by cars and yet it only slows me a .5 sec clip of me getting in the car... It's done this every single time. I have a SanDisk MobileMate USB 3.0 if that matters.. Anyone have any advise??