Unity assets’ 3D models break in Godot due to incompatibility with Unity-specific formats (e.g., .fbx with proprietary metadata) or engine-exclusive features like shaders, animations, or materials.
The root issue is that Unity assets rely on tools Godot doesn’t natively support—such as Unity’s Standard Shader or animation controllers—causing textures, rigs, or interactions to fail.
To fix this, export models as generic .fbx (no Unity metadata), rebuild materials with Godot’s ShaderMaterial, or use community converters for compatibility.