ComputeWorldVertices() does not compute any UVs. UVs are static, except if an attachment is clipped. Ingoring the clipping case, the results you get for RegionAttachment and MeshAttachment ComputeWorldVertices are exactly the same.
I would suggest to start with a simple skeleton, e.g. just a single RegionAttachment without any animation. Work your way up from there.
You can also share your code here and we can try to identify the issue.
