A subcontractor sent a large assembly file that was created in Libre3D. He sent them both as single .step file ( and as a single .x_t file. I've tried opening both (separately) in SolidWorks Premium 2025 SP3.0. The .x_t files seem closer to working (it opens an entire tree which can be viewed in the Feature Tree, components hidden and shown, etc). When I go to save this assembly file, it saves most (if not all) of the components and subassemblies, but does not save the top-level assembly file. It gives me an error, "Failed to save document."

I'm not really sure what to do with that. If there is a corrupted file or something, how would I know which it is? How do I proceed? I wasn't given any kind of error other than that generic error. Solidworks shows me the whole assembly file as far as I can tell, but it cannot be saved. I need to make a drawing from it.