When using First-person Model and MCA it will render the my head when looking at my roommates account. It also will un-render his head.
This does not happen with my other friend who does not share a room.
I tested this issue with just MCA, First-person Model, Not Enough Animations and Skin Layers 3D on minecraft 1.18.2. Forge 40.1.68

Fixed via 7.3.21's playerRendererBlacklist Setting, as certain RenderLayers can now be disabled with different mods if they overwrite the same things we do.