As it said in the title, all pulsing malachite blocks are transparent except it's pattern and you can see through it as if you were in Spectator mode.
Minecraft is 1.15.2, forge is 31.2.33, Gaia Dimension is 1.2.2

Can I get a screenshot? I haven't seen this happen in my environment.

Sure

I've been unable to reproduce this. Are there other mods that might alter rendering, such as CTM, or other additional modifications like Optifine?

Considering the screenshots show other mods installed, I may advise checking over the mod list for culprits. Remove half the mods, load up and check if the error exists, and continue until a small handful are left

Closing due to inactivity. Verifying the issue has not been successful.