Set Master Pose is breaking skeleton

I’m trying to create a modular character; one in which I can swap out parts to allow customization.

I got everything into the engine successfully, but when I try using Set Master Pose Component to link the various skeletal meshes into a single character, the skeleton breaks down and mashes up the arms and legs.

Here was my approach.

I brought the UE4 mannequin into Maya LT 2018, and split the arms, legs, torso, and head into separate objects. I used Quick Rig to bind them all to a single skeleton.

First I imported everything together as a single character, in order to get the complete base skeleton and physics rig.

Then I imported each object individually as skeletal meshes, each assigned to use the base skeleton and physics rig from the complete character I had first imported.

Then I used a character blueprint to piece all of the objects together into a single character.

Inside the blueprint I set the torso as the base inherited mesh, and added the various limbs as additional skeletal meshes. So far, so good.

But when I try to use Set Master Pose Component to link the limbs to the torso so everything works and animates together as a single character, the skeleton breaks.

Whether I use the construction script or the event graph, once this node runs it all goes to crap, and I have no idea why.

Inside the node I set the head, arms, and legs as the target, and the inherited mesh (torso) as the master.

If it matters, I’m using FBX 2016 format. I tried using 2018 at first, but that caused things to break down before even reaching this stage.