Duplicate registry key crash: 'minecraft:armor_material/minecraft:copper' registered twice by Copper Age Backport itself (NeoForge 1.21.1, large modpack) · Issue #107 · Smallinger/Copper-Age-Backport
Description Game crashes during mod loading with a duplicate registry key exception. Both stack frames of the duplicate registration point to Copper Age Backport's own code (CopperArmorMaterial.cre...