Show Me Your Skin 1.7.0
Wildfire's Female Gender Mod 3.2.1
Minecraft Version 1.20.2

Armor rendering has changed in my mod's latest version, causing your Mixin to fail and crash the game. It was separated to it's own GenderArmorLayer.java class to allow rendering on more than just PlayerEntity models (i.e. armor stands now).

WildfireRomeo/WildfireFemaleGenderMod#163

This is most likely the new method you want to Mixin.
protected void renderBreastArmor(T entity, MatrixStack matrixStack, VertexConsumerProvider vertexConsumerProvider, int packedLightIn, boolean left) { ... }

The crash is only on 1.20.2 not 1.20.1

I've disabled the compat module for now, to at least prevent a crash. The code I'm targetting seems to have changed significantly, so I'll have to reconsider how I'll approach compat.

Fixed as of 1.9.0.

Ah, thanks for letting me know. I'll push an update soon. Is this only changed post-1.20.2, or is 1.20.1 or lower affected as well?