Here are two FBX models which are identical in every way, except one has an additional shoulder Mesh Object, which, for some reason, messes up the imported position of the other two Mesh Objects.
All three Mesh Objects are using vertex groups, which I think is somehow central to this problem, but not sure how.
If you import the without_shoulder.fbx, you’ll see the correct position the other two Mesh Objects should be in.
When you import the with_shoulder.fbx, you’ll see the incorrect position those two mesh objects get moved to which is the origin (0, 0, 0).
I’ve been trying to figure this out for days, and I’ve narrowed down the problem as much as I can to just being isolated to this problematic Mesh Object.
Link to zip file containing with_shoulder.fbx (problem file) and without_shoulder.fbx (reference file to see correct position):
https://drive.google.com/file/d/11AHzjB3d5g6TzteuvKrHpwDoSsZqNSEm/view?usp=sharing