On my first automated flight with Phantom 4 RTK, I had a soft crash landing.
All of a sudden, while hovering about 15 feet in the air, 30 feet away from me, it started sliding sideways.  

Fortunately, I could bring it down into the grass with just a minor tumble and no damage.

What happened?

I have flown P4's for years, and use S mode to land when changing batteries or ending a mission.

This time, the S position on the mode switch took the drone into ATTI mode instead.

The problem is repeatable.  DJI Pilot app on Android clearly reports ATTI mode when the switch is in the S position.

When I hook my regular Phantom 4 Pro and controller to the same app, it (correctly) reports Sport mode when in the S position.

Has anyone else encountered this?   
I don't think it is a hardware problem, because the controller "peeps" at each mode position (P, S, A) but the Pilot app only shows change of state between S and P.. not A position.

Keith

Hello, there. Sorry for your inconvenience. Please kindly note that the aircraft will automatically enter the ATTI mode if the GPS satellite signal is poor or the compass is interfered. And the visual positioning function is disabled due to the condition does not meet the effective requirements.

There is no reason to switch to S. It doesn't matter if you land in manual or automatic mode, stay on P. And moreover, if the RTK correction is done on takeoff, and it is still valid on landing, you have nothing to do. Let it land on its own, it will come back from where it took off. Land in an open space and preferably on a flat surface. the drone detects if the relief of the surface is not suitable.