I have posted this same forum thread in the sketchfab forums, since posting these 2 threads I have resolved the issue though the bug can still be recreated.
The bug is seemingly caused by adding a diffuse map as a color on your material, its perfectly fine most of the time, but suddenly you add one more and this bug appears. On one instance removing that material and replacing it with a fresh lambert fixed it, on another case I had to remove every single material that had a diffuse map and replace them with just basic grey lamberts for the bug to go away.
The most frustrating part is that if you google this bug you find a couple of threads like mine, but none of them ever get solved, nor do the people respond and say that it was fixed.