Ok I flew my phantom to 50% give or take. Then I loaded it up and went home. I was on the deck and fired it up but camera didn't work. So I shut it all down and restarted. Camera worked had 11 on gps so I thought I would just hover to run battery down. The alarm goes off at 30% so I continue hovering. Now my phantom starts moving, so I try to pull the t back and nothing. I was hovering maybe 8" off deck. So I try again to pull it back( I am flying in a 3' square area were I take off and land) and still nothing, I push forward nothing back nothing, land nothing, I start getting scared and go to grab it and I'm still pulling down on the stock and it lands. Do I need to do a imu, gps or was my battery too low and the machine just got confused?
I'm taking it out to the lake tomorrow and I have put over an hour and about15 mins of worry free flying. Did I do something wrong?

Forgot to mention that the obstacle avoidance was lighting up

Hello rheaps, did you see any error message from the app at that time? You can check it by playing back the flight record in DJI Go app. If it is convenient, it would be better to download the DAT file of this flight via DJI Assistant 2 and send it to support.us@dji.com for data analysys. What's more, please do an IMU calibration and compass calibration before your next flight.

We are just leaving on holidays so I will down load the data on Tuesday. I will do an imu and compass calibration before next flight. Thanks

If you are flying in a 3ft square area with obstacle avoidance on then you will not be able to move forward. The aircraft will stop when it reaches 6ft of an object. It's probably not safe to fly in an area that small with avoidance on. If you turn it off then you can fly with no problem BUT you really should not be in that confined of an area.