Need some advice pls.

I have the latest firmware and I plug my OnePlus 5. Did my preflight check. No warning or error,took off. Problem started, the drone start rising and rising about 12metre high, i start to find it strange so  tried to use the remote control to lower it by pulling the left throttle  down (mode 2) but there was no  immediate response, then after a few seconds later, it start to lower it self. Without my input to the remote at all, it start lowering it's altitude itself slowly then it hit the ground and stop once the propeller hit the grass.

A moment ago,I tried to calibrate the controller but it was not successful. Now I don't really know what's wrong so anyone has any similar experiences? Pls share and advise, thank you.

Probably what happened  is you pushed the left stick down too hard and you initiated a landing.

Best thing is to read the manual, practice in the academy and then fly in BEGINNER MODE until you get better.

Giver us your FW on both the AC and RC and the / APP version. Also did you get any warnings?

You might also check the downward facing sensors to be sure they are clear of debris and clean. How did you initiate takeoff?

Thanks for responding. There was no warning or error. The drone is new and clean. Looking at the log, the drone took off and with no input, kept on rising. Full downward position on left throttle to bring it down was produce a slow desend. I am pointing at phone incompatibility for now. Till I do further testing.

Please try to calibrate the RC and make sure that all firmware had upgraded. If the drone is still acting the same, please contact our support team to start a data analysis: http://www.dji.com/support.