I was flying the mavic earlier (weather was good and very little wind), and captured some video footage.  When examining this video later, I noticed a couple of weird issues that I've not seen before.  Once was sort of "interference" in the video frame, while the other seems to show the video going completely out of focus and the gimbal trying to do a recalibration.  I also notice that the gimbal always vibrates quite a lot during decent.  
Drone was in normal (non-sport) mode.  Gimbal protector dome was on.  

Is this a common defect, or do I have a defective mavic?

Hello, did you crash the aircraft before? Is the firmware up to date?
Please try to do the IMU calibration and gimbal calibration.
As for your first video, it's the shadow of the propeller.  Please do not shoot into the sun, or tilt the camera down more.

DJI Mindy Posted at 2017-1-9 00:07
Hello, did you crash the aircraft before? Is the firmware up to date?
Please try to do the IMU calibration and gimbal calibration.
As for your first video, it's the shadow of the propeller.  Please do not shoot into the sun, or tilt the camera down more.

Thanks for clarifying Mindy.  I never realised this was the prop shadow, I assumed it was some sort of camera interference.  Feel a bit stupid for even reporting it now.  I'll happily ignore this when I see it from now on.

Regarding the other issue with the gimbal, it's the first time I've ever seen this happen, so it's probably a one-off.  Just prior to this problem I did get a "gimbal reached max attitude" error, so maybe the flight movement was too acute which caused the gimbal to shake.  I'm on the latest firmware, and did a full firmware refresh last week.  Also done full calibration.  Gimbal calibration completes fine.  Did have one very minor crash indoors a couple of weeks ago, but it only chipped a prop and fell onto soft furniture, and it's been flying fine since then so I don't think any damage was done.  I'll report back if it happens again, but for now I'll just assume it was a random glitch.  The mavic was flying great yesterday despite this small gimbal issue.

fans707604b2 Posted at 2017-1-9 04:25
Thanks for clarifying Mindy.  I never realised this was the prop shadow, I assumed it was some sort of camera interference.  Feel a bit stupid for even reporting it now.  I'll happily ignore this when I see it from now on.

Regarding the other issue with the gimbal, it's the first time I've ever seen this happen, so it's probably a one-off.  Just prior to this problem I did get a "gimbal reached max attitude" error, so maybe the flight movement was too acute which caused the gimbal to shake.  I'm on the latest firmware, and did a full firmware refresh last week.  Also done full calibration.  Gimbal calibration completes fine.  Did have one very minor crash indoors a couple of weeks ago, but it only chipped a prop and fell onto soft furniture, and it's been flying fine since then so I don't think any damage was done.  I'll report back if it happens again, but for now I'll just assume it was a random glitch.  The mavic was flying great yesterday despite this small gimbal issue.

Thanks for your update. If you have any further issue, please feel free to let me know.