I have been using my Mavic Air and I dont know how to get rid of that choppy video.
I have a SanDisk 64gb extreme. The video was recorded at 4k 30 fps.

Hi, sorry for the inconvenience, the video that you provided is unable to be checked, could you please provide the video again? Please check all the original videos from the SD card to see if all the original videos have this issue or not?

I am sorry, i just noticed my video was private. But now you should be able to see it. And yeah pretty much all videos look like that, mainly when panning.

Get some ND filters. This is a great video on the topic.

As above.  If you look at any single frame from the video it is very sharp, great for taking stills from the video, but giving the "choppy" flipbook effect.  Even at 30fps your brain is able to make out the "jumps" between each individual image, however small.  An ND filter (or stronger than you were using) would slow down the shutter and introduce a touch of blur, blending the individual frames together for a silky smooth look.