I can and do fly my Phantom 3 Pro, regularly inside of an old vacant aircraft hangar. Our city centre Municipal Airport has for several years been closed. Next door to our Aeronautics Museum, this building is predominantly metal, with a lot of steel reinforcing girders all along the ceiling. There are lots of metal ducting, conduit, high power wiring all over the place, HID lighting across the ceiling. We have never-not had a great GPS lock, even with all that metal surrounding the drone, & still have a very regular connection to 15-18 Sat. It drops off at rare infrequent times, but generally stays Locked On. And drifting is barely visible, seriously, it doesn't move around much at all. So far, I only had one Compass error, in there, from rebar in the concrete floor, but moved the Phantom only a few feet over, and it was fine ever since. Yeah, wow, these drones are magnificent. Well mine most certainly is anyway, I can't speak, but for only a few others, locally.
If only we could all everyone, happily share these expectations & experiences. Satisfaction guaranteed. (Or send it in for repair...)
Yet, others can't get theirs to work, right out in an open field at the local country side...
Go figure. (?)
RedHotPoker