This seems to happen if you have mesh and interior material set to same value.
Here my solution for all my PhysXLab DMs:
- Run version 1.3.2 (it seems to be far more stable).
- Under File, Import 3D Mesh (Alt+I) and select your FBX file.
- Under Tools, fracture mesh (no need to change settings yet).
- Under Graphics, and in Material Library tab you will see green/white lambert.
- Right click lambert and load texture as material.
- Grab targa file you want for your mesh (or any really, you can change everything in UE later)
- Select your new texture in Material Library tab, then under Mesh Materials tab click apply (black) arrow.
- Now, under Interior Material Selection tab select lambert and click Set Interior Material of Selected. (You may see this result after you apply your mesh material, but I would still recommend you do this to make sure)
- Set U Scale and V Scale to 100 or whatever your scale needs.
You should now see two different textures applied. Finish rest of your settings, export asset, and after you import into UE you can set textures as you need them to be.