This issue is still persisting (the Greyhawk always wanting to land when releasing controls), it is a real pain, especially since there is no known way to fix it, when it happens say good bye to your UAV, even if you let it land as soon as you get back in the air it will land itself again. I also ran into a similar issue where by the Greyhawk just started flying north every time I released the controls, despite any waypoints i placed. I believe it also stemmed from mucking with advanced waypoint controls.

I am surprised these are still issues well over 12 months after being reported.