substracting one mesh from another

Hello.

I have the path of a road in a mountainside (delaunay mesh). That path is represented by a loft which was extruded (and converted to mesh) to remove such volume from the slope. (so, both are meshes).

The thing is nothing seems to work. I've tried with "mesh difference", "Mesh split",  and giving thickness with weaverbird and then tried to subtract. Nothing.

Tried "Mesh intersection", but it is like both meshes failed to intersect when they actually do.

Any idea what I'm doing wrong? 

Thanks

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