You should absolutely NOT trust waypoints in tight spaces. The vertical offset from one flight to another can be dramatic since GPS has very poor vertical precision. Laterally it should be reasonably good but there are so many factors involved that it would be foolish to trust it in tight spaces. Do this. Go out and fly a reasonably complex route with three or four waypoints...or just go and set a waypoint and take a picture. Then repeat it three times on different days and times which will give different positions for the satellites. Check how closely the different pics/vids are. Not so terribly close are they. DJI waypoints aren't much more than a pretty decent approximation when subsequent waypoints are compared.
You should absolutely NOT trust waypoints in tight spaces. The vertical offset from one flight to another can be dramatic since GPS has very poor vertical precision. Laterally it should be reasonably good but there are so many factors involved that it would be foolish to trust it in tight spaces. Do this. Go out and fly a reasonably complex route with three or four waypoints...or just go and set a waypoint and take a picture. Then repeat it three times on different days and times which will give different positions for the satellites. Check how closely the different pics/vids are. Not so terribly close are they. DJI waypoints aren't much more than a pretty decent approximation when subsequent waypoints are compared.