Can you please share the links to the models with this issue so we can have a look?
I suspect it’s related to precision issues when we compress vertex positions during processing. This can happen in models where the total scene is very big, but there are small details compared to the bounding box size. Or, models with very big and very small polygons. Or, models that are very far away from the origin.
I can try reprocessing such models without compression for you to see if it helps. There may not be much you can do on your end, but we’ll take a look!