Could you upload that test model (c4d file + texture) somewhere, so that others can test the import too? Cannot download the sketchfab file ^.^ For my imports i modified the master material a little bit, but i also use an ancient C4D R15, which is the last version without PBR, so i would not want is that as a reference. But since your model does, a comparsion would be possible, to see, if it gets imported the same way as my files from the older versions.
One thing i see, your sketchfab file says for PBR, that it uses specular workflow, as far as i know, UE uses metallic workflow.