Been trying to set the Failsafe return to home altitude.... the box shows a range of 20-500... I set it at 50m, and it accepts it, then immediately changes it to 0. No matter what value I put in the box, it seems to not want to take it, and changes it back to a 0. Obviously, 0 is pretty scary - what do I have to do to have the app accept the value I put in?