Flown 10 flights without issue, This one however resulted in what you see in the video.
Gimbal goes whacky, seems to move through a reset pattern. Once it stopped the horizon was off, so I reset that, then flew forward, for it just to do the wierd reset again. It flew just fine for 15 mintues afterwards and landed fine, checked the Gimbal and as much as I can tell it looks fine?
Weird, that does look like the reset pattern. Were there any gimbal errors in the flight logs?
Maybe try a gimbal calibration and see if this behavior occurs again.
I haven't had a chance to look at one closely ( mine is still 6+ weeks away).
The early Phantoms had a minor problem of the small flex ribbon to camera/gimbals getting loose.
Maybe a gentile re seat would help.
I had the same problem with my drone and unfortunately I had to send it in for repair. It took me a week for ground shipping to send it to their repair shop from the east coast. Once they got it though they evaluated it and repaired it within a day and said that the aircraft/gimbal had software/hardware issues and they fixed it under warranty. They said it will be shipped back within 3 buisness days so I'm hoping to get my drone back soon. A lot of Mavic's have been having this problem and it's unfortunate but you should probably send it in for repair if you have tried everything and are still having the problem.
I had a somewhat similar issue the other day. The gimbal didn't move all around like yours did but it was quite wobbly for a while. After it settled down, I haven't had a problem since but I've only done a few flights.