Minecraft v1.15.2
Forge v31.2.36
ZYCraft v0.1.0

Aluminizied Engineering Blocks have z-fighting, but only on some x or z coordinates. Optifine is not installed. It can be replicated without any mods installed (besides the required mods), but is much more pronounced if Minecolonies is installed.

Ah, yeah. I saw that myself when debugging mod, for me it happens on the chunk borders. It also happens pretty much on all my blocks. I don't know what causes it because I use 100% Vanilla models. Not sure what I can do about it at this moment, will investigate in the future!

Alright, thanks!