public SecondarySpriteTexture[] SecondaryTextures { get; set; }

Swapped sprites are cached statically so they can be shared between instances. Unfortunately, the cache isn't tied to secondary textures so if multiple instances replace TextureA with TextureB and have different secondary textures then they would interfere with each other. That's unlikely to be a real issue because TextureB should always have TextureBNormals as a secondary texture. It would be possible to avoid this if necessary, but doing so would cost more performance and increase the complexity of this system.