So i deleted the non deformer history (after deleting the faces) and finally managed to export the fbx with autodesk media entertainment settings with ‘input connections’ unticked. This seemed to work. I then import the fbx into unreal and choose ‘metahuman_base_skel’ as the skeleton. It then says ‘FAILED TO MERGE BONES’ This could happen if significant hierarchical changes have been made, etc…this may invalidate animation data etc