...and yet it still won't let you change altitude.
I programmed a mission by flying it first, and setting waypoints by drone's position. This included a pass under a rather low bridge over some small rapids.
Unfortunately, when I flew the mission, the entire thing was about 1 foot higher than I had programmed. When it came to the bridge, the collision avoidance kicked in and stopped the drone. I paused the mission, and found I could back up, yaw, but NOT change altitude. Really peeved about that. I wanted to manually fly under the bridge again as I had done earlier, but until I stopped the mission, I couldn't change altitude.