thanks for the details!
The issue with our processing is identified, however the right fix for it is not, yet.
If you want some more details, we compress 3D data with both lossy and lossless approaches to optimize model loading time. The issue here is that our lossy algorithm is too aggressive on your model geometry (this explains why you did not notice the issue on your other models) and destroy too much information on the UVs. I'm able to improve this a bit but it's still not perfect and that's why no fix has been released yet.
What's difficult is that we don't want to overoptimize the compression for a small class of models and have a larger class of models being less compressed and thus heavier to load.
Rest assured that Sketchfab aims at delivering high quality content so I'm working on a fix but it might take me longer than wished. I'll let you know when the good fix is live!