HeroMaterial redefinition error
If you receive a HeroMaterial Redefinition error in the error panel, then you have 2 or more materials with the same name.
Once a material is loaded, it uses those settings. So if a second material is loaded with the same name, but with different settings, the engine will ignore them and use the set that was first defined. The error will tell you exactly which setting is wrong. It is then you job to either give one of them a unique name or make their settings identical, whichever is more appropriate for you.
For help learning how the Hero Material system works: Hero_Material