Follow me uses GPS to track. It's lagging behind your actual position. One possibility is lag in the gps location reported by your phone or tablet.
ActiveTrack processes the image. If you are close, and move quickly out of frame, it can get fooled and lose you, which is what happened at the end. Contrasting colors help activetrack to do a better job.
I can't say much about the image quality because the video resolution is so low. It looks like you adjusted the exposure at some point so that things were blown out, and then set it back again. Hard to say much more.