Relaunch Blender and confirm all modifiers are applied to your mesh, especially those affecting topology or UVs like Subdivision Surface, Mirror, or Array. Ensure all transforms (location, rotation, scale) are applied via Ctrl+A in Object Mode to prevent scaling or rotation discrepancies in Unity. Verify your mesh has valid UV maps and no overlapping UV islands, which can cause visual artifacts. This ensures Unity correctly interprets mesh data and UV coordinates, preventing misalignment of bolts and seams. Exporting as an intermediate OBJ then FBX often cleans internal Blender data corruption affecting UV channels during direct FBX export.

1. Export your model from its original Blender scene as an OBJ file. Set export options for Selection Only and Apply Modifiers. Ensure Include UVs is checked.
2. Launch a new, clean Blender instance to avoid potential scene-specific data issues.
3. Import your previously exported OBJ file into the new scene. Verify UVs and geometry integrity.
4. Export your model again from the new scene as an FBX file. Configure the FBX export: set Smoothing to Face or Edge, ensure Apply Modifiers is enabled, and Baked Animation is disabled unless explicitly needed. Check Mesh and Armature options if applicable.
5. Import your newly exported FBX file into Unity. Check the Model tab in the Inspector for Generate Lightmap UVs if static lighting is required, and verify Import Materials settings. This process enforces a clean transfer of mesh data, UV mapping, and normal information.

Additional Tips

• Use the Triangulate modifier in Blender before export to ensure Unity does not create different edge turns that distort UV layouts.
• Ensure that only one UV map exists in the Data properties tab before export to avoid Unity indexing the wrong map.