Strange color artifacts in rendered video

Watching that, I was seeing some macro-blocking going on especially in some of the 'general' shadow areas, those place with a smooth surface. That's due to the way long-GOP compression works.

It looks at blocks of pixels, something like four, six, nine, whatever ... and if they are all pretty close ... say something like 25/29/42, 25/27/43, 23/29/44 ... it will probably 'simplify' data keeping by making them all just 25/29/42.

So slight gradients get lost, and you get adjacent pixel blocks of slightly different tone.

Which is where Averdahl's suggestions save your bacon ... and your pixels!

I think I've resolved the issue by exporting the video as HEVC (H.265) instead of H.264.
https://vimeo.com/1146681233?fl=pl&fe=cm

You don´t provide the setting you use, but i say use a higher bit rate, for Bitrate Encoding use CBR, under Advanced Settings check the box and change the value from the default 72 to match the frame rate you export to. If you export to 30 fps, set this value to 30.

How does it look if you export the same scene to Apple ProRes LT?