When playing with Optifabric the armor layer of the models from Customizable Player Models don't render correctly, rendering the vanilla armor. Unsure what happened as it worked in 1.17 but since 1.18 it has broke. This has also been posted in that mod's corresponding issue tracker and someone mentioned it seems to be Optifabric

With Optifabric:

Without Optifabric:

Unsure if this is something that can be fixed easily if at all, but I do hope that it is.