Indeed there are 2 versions, one posted on Sketchfab (using the exported .dae format), and an older one from ArtStation (exported in .fbx format).
The problem with the .dae version is the use of different materials for the same meshes, causing overlapping conflicts.
I was forced to import the .dae into Accustrans, and save it as an .obj file, because C4D was unable to process the original Sketchfab file correctly. Once converted to .obj with Accustrans, i had to get rid of all overlapping meshes and sort out the many normal errors with C4D.
I have completed most of this tedious work, and i should be able to produce a custom texture set for the Sketchfab version, this is what i am working on right now
