Reimporting of skeletal mesh results in a scrambled skeletal mesh

When we reimport our skeletal meshes with updated FBXs, the resulting skeletal mesh is scrambled up. See Scrambled.jpg attached.

This does not affect every single reimport but happens randomly.

We are using the legacy importer due to issues we have come across with interchange. See this ticket [Link Removed]

I have managed to work around the issue by reimporting with dialog and clearing the skeleton and then deleting the new skeleton and replace the reference with the old field but this has not worked every time.

Disable interchange for FBX import with the following command "Interchange.FeatureFlags.Import.FBX 0"

Import [Link Removed] attached FBX

reimport with new file and point at [Link Removed].

You should see a result similar to "[Link Removed]".

There are no blendshapes in the FBX. It has 259 bones which have the same hierarchy.