How to fix stretched materials on geometry collections?

Fractured Geometry Collections will experience material stretching. This material is from TwinMotion and is UV independent. So in theory it should maintain a consistent appearance even when fractured.
But the result is not. It looks as if the UVs have been compressed horizontally.

And I tried the inner material assignment but it doesn’t seem to work. (I thought I could fix it there)
The official documentation says that Element1 and Element3 are assigned to the internal material, but thay both use Element0. Maybe the documentation is out of date.
How can I make the inner materials look normal?