Answering some of the questions above.
@ Bsnub. The Mavic does remarkably well with buildings and obstacles due its front sensors. However with any drone line of sight is best. I usually don't fly in between buildings. I fly above then and pan down with the gimbal knob.
I have flown my drone well over 2500 meters away on a few occassions. I have also flown it up over 1000 meters. Some of the Vids I shot over Koh Samed yesterday were 500 to 600 meters up.
If the Mavic loses signal or GPS connection it will do a few things depending on circumstances. It will try and reconnect. Usually hitting RTH it will come back to compass settings. If it cannot connect it will land where it is and battery conditions. If you lose it you can do a log track in remote and usually find it. There are guys online that you can send your log files and they will help. Of course of water you are SOL..your mavic is trash.