Compression on still images placed in video, night sky

I'm doing some testing for night shots. different exposure lengths in different lighting. This particular shot is 30 seconds at ISO 100. I'm happy with results, I could improve with manual stitching and some brightness correction at the seam, but that is the nature of dual lens with uneven local lighting. I did shoot some test with lens aiming up.

So the reason this is posted under VirbEdit, is why even max or custom setting for quality produced very bad results. I've done some night/sunset shots from movies and not seen this, wondering if its because still is being converted to movie (poorly). It looks fine in editor and preview, just not in exported movie. May Make make into movie elsewhere as test.

Of course I can't upload photos :( Same errors as always. Here it is on google photo
https://photos.app.goo.gl/NSlVxM4BfpPxhXjl2