gps lock

I've noticed that occasionally when I start my Phantom up inside my work shop that often times it hovers perfectly in place and other times it tilts (usually forward) and takes off flying at a walking pace. It is never locked onto GPS indoors (steel building) but why would it decide to take...

Hi guys, not getting any satellite signal on my DJI Vision app, this has happened twice now. Cant get any lock onto satellites and so just getting to play but no gps assistance. Any ideas?