Cached Quads appears to select random blocks from within the chunk. These random blocks also seem to randomly change on occasion.

Cache Quads caches the most recent quad with a real texture. I can update this to only cache smoothable block quads with real textures, but as it says in the tooltip, its a fix aimed at patching small hiccups in the algorithm - not fixing a pretty much broken one. I'll still see what I can do tho

I also seem to get this issue with SurfaceNets 5:
First I noticed Bedrock randomly placed when digging some blocks:

Then I reloaded without NoCubes and RenderChunkRebuild to proof the misleading blocks:

And then I loaded back in with NoCubes and now there are normal blocks and graphical glitches:

Here's my config:

Cache quads has been removed in 1ee0aa3