Eliminate compression artifacts from high contrast subjects?

[XilburQost]

I am creating computer animations of space scenes which feature brightly lit planets and spacecraft against black backgrounds. The animations are rendered as individual PNG-format images (one image per frame) that I import into Premiere Pro and export as MP4. The issue is that the resulting MP4s display what I believe to be compression artifacts; they resemble sprocket holes or railroad tracks (see attached). Is there a way to eliminate this?
I'm exporting as HEVC (H.265) / Match Source - High Bitrate

I get better results if I export as HEVC (H.265) / 4k UHD, but the artifacts are still there, albeit less obvious, and the file size increases 10x. 
Any suggestions? Thanks. Premiere Pro 22.2, Windows 11

[chrisw44157881]

render out a 10 bit intermediate file. perhaps you could try a 10 bit h.264/5 with CQ quality at 18 with handbrake. if you're uploading to youtube, try cineform low as it uses wavelet encoding.