These lines appear on dirt and gravel blocks all the time.

I tested both Stay True and DOO, one at a time, together, and with Vanilla Experience+, and I was not able to reproduce this. Please provide your full list of resource packs and mods with versions; the easiest way to do this is to send your log file.

Which resource packs are you using?

I'm using a bunch. What I've got it down to;
Stay True and Deep Origins Overlays both lead to this. I'm fine with leaving out Stay True, as I'm also using Vanilla Experience+, but DOO is the reason I got Continuity, and it's strange that they do not work properly together, when it's literally a requirement.

Hi! Here is the log file
latest.log

You have so many resource packs it would be difficult for me to test this myself. If you are still interested in debugging this, try removing resource packs one by one except for Stay True, DOO, and Vanilla Experience+ until the issue no longer happens or until all packs except those have been removed.

Same happens with the sides of soul soil to netherrack. It looks like netherrack is trying to reach over the soul soil and vice versa.
Same happens with nether quartz and nether gold ore instead of netherrack.
Soul sand doesn't seem to be affected with this.

Similar issue here though not the same.

Forge 47.3.0
Continuity 3.0.0+1.20.1

I have a minimal mod list.
Botania
Botania Garden of Glass
Continuity
Essential Mod
Forge CIT