Datasmith re-import, one mesh won't take it's previous material

Thanks. I read something like that but wasn’t sure about how it works in practice. I’m now discovering how to use materials correctly, whether on the geometry or the reference in the level, along with material instances.
The Datasmith re-import process does seem a little flawed though. I’ve just discovered something else that’s not working as I understand it should.

I made changes within my max scene and re-imported the whole Datasmith file, without materials or textures.

Image 1 is how it came in. We are looking at the line of balcony sections with chequers. They should have the same timber floor material as the corner, a duplicated and edited Unreal material.

I selected the asset, reset that element material to chequerboard, re-applied the timber slat material, and here is the result, it’s not visible on the mesh.

Strangely, if I add any other duplicated and edited material from my Unreal scene, it does become visible.

I do not understand what’s happening here. I read Felix’s comments on another thread about making a duplicate and re-applying to re-imported assets, but what’s happening here?? The whole scene was exported. Only models I altered or added were imported without materials, as I expected them to. They take their materials from Unreal just fine

I’ve re-imported the datasmith file, with materials applied, and it’s still the same, just this one element of this geometry isn’t showing.

Hello,

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Thanks