I was flying my P4 along a river and climbing slowly, I then decided to climb a bit quicker to get a more expansive shot and heard the motors go to max. P4 was about 240 metres along the river at this time. I released all sticks and watched as the altitude kept rising rapidly. DJI Go app announced maximum altitude reached. The p4 continued to climb. I lost sight of it and watched altitude and distance measurements increasing. From memory it was about 260 metres high when I activated RTH and still distances continued to increase. Switched of RTH and manually tried to bring P4 home. It started to respond and once I got a visual on it I tried RTH again. It flew straight back over me and started descending. I noticed it was coming down way faster than I have ever seen my P2 descend. Fortunately I cancelled the auto land function in time and managed to just pull the P4 up before it would have slammed into the ground. Any thoughts on what may have gone wrong? I had noticed that when doing a low altitude auto land it landed a lot harder than my P2 ever has. Can anyone explain what they think may cause this.? I have stood straight under the P4 and lowered it to see if the sensors picked me up. They did not. It was within 2 feet of my head which I assume would indicate sensor calibration issues or faulty sensors. Any thoughts?