I have had an issue today, that I am unable to Enable Vision Positioning. When I push the slider to enable it, it immediately snaps back off. RTH Obstacle Check is ON, Enable Obstacle Avoidance is ON. Flying in "P" Mode. I am operating with iOS11, and upgraded software and firmware last week, no new upgrades are appearing on my DJI Go4. Anyone have an idea what I'm missing, or doing wrong? Thanks for any help.