Auxiliary leaf resources (TEXMAP PNGs, LDConfig.ldr) were being directly admitted to the resolved closure AND queued into the BFS children queue. When dequeued, the generic per-node path admitted them again, causing ResourceClosure::validate to reject with 'duplicate resolved resource identity' (HTTP 400). Fix: push aux resources straight to the resources collection instead of through the BFS queue. They are leaf assets, not LDraw graph nodes to inspect recursively. Epic: PM-86