Trying to split the ue4 mannequin

Trying to follow along with this video

which is a bit old, but instead of importing animations from mixamo, I’m just trying to take the base ue4 mannequin, divide it up in blender, and then reimport these segmented meshes into my project and attatch them all using the “set master pose component” node. However, when I import a segment of the original mannequin (with the original rig still attatched), I go to replace the skeleton on the animation sequence, and I end up with a very scrunched skeleton
muh back

Modeling isnt exactly my area of expertise, so I may be missing something. Any thoughts on what it could be?