Hi Merhlin, if you have been watching this thread you will know that you aren't alone in the shimmering gravel stakes. There is something about the size/detail in gravel that causes anti-aliasing artifacts in a number of the videos posted. Since I don't have a drone to test, I can only surmise what the cause might be and how it might be fixed.
1. Drone speed
The faster the camera is travelling the more likely you are to see artifacts. When the frames change so rapidly over a short time, it's a big ask of any camera and any recording mechanism to capture details faithfully. So, for best quality video, fly slowly.
2. Fast pans
For the same reason, a camera which is panning rapidly will struggle to capture all the detail. So pan slowly.
3. Camera settings
Any Auto camera settings, such as Auto White Balance, add a further layer of complexity as the filming conditions change. So, if possible, use manual/static settings and, if necessary, make adjustments to the video in post.
4. Subject matter
Obviously there is more detail in gravel than there is a flat, solid surface. If, after adjusting for it, it still causes artifacts, don't film it.
5. Capture + Frame rate
Data will be dropped if the bitrate and capture card can't cope with it. So make sure you are using the fastest, reliable memory card you can buy; and you will tend to drop more data when filming at the camera's maximum potential capability, ie at 4k and/or at 60fps. So, if you don't need 4k or 60fps, don't film in them.
6. Compression
There has been a lot of discussion here about the damage done to video by different codecs and compression rates. Your video is compressed in the camera to H.264 and you may, after editing, compress it again to save or export it. Then, when you upload it to YouTube it gets compressed for a third time. Data and detail are dropped each time. So, do your research (including in this thread) on video compression and how best to upload to YouTube…and consider less aggressive alternatives to YouTube such as Vimeo.
The above is based on my observations. I am not an expert and nor am I an experienced videographer. I am envious of your drone; and your video.
PS. And as Ron implies, don't over-sharpen detailed subjects in post. Sharpening doesn't have to be applied at the same level across the whole frame.