I recently purchased a model from sketchfab that included animation. The model opens in blender without issue, exported to gltf fine, and imported to Godot properly. It displays statically and animated in the editor, as well as when exported on the PC, iOS 11.3, iOS 14.4, and various versions of Android.
However, when running on iOS 12.5.1, the model does not render correctly, like the vertices are out of order or are moving around, or have incorrect normals. I've narrowed the issue down to the armature, as when I delete the collection containing it within blender and re-export the model, I no longer have the issue.
Really just looking for any direction at this point, as aside from "something with the armature", I'm a bit in the dark, and obviously don't want to lose the animation on the model.
Here's what it looks like within blender:
I don't know enough about modelling and rigging to know whether there's anything obvious about the structure that could be causing the issue, nor what quirks iOS 12.x might have in relation to it.