Multiple root bone error when importing baked Metahuman facial rig

For a university project we want to use the Metahuman facial rig on our own characters. So far I have managed to detach the head joint from the Metahuman neck in Maya and attached it to a root joint at the centre of the world. I have also managed to import some mocap animation from LiveLink and applied that to the Metahuman facial rig which also deforms our own custom face mesh.
I baked this animation onto the joints and the custom geometry on a new animation layer then exported only the joints and geometry as an FBX with the animation. The only thing now is it won’t import into Unreal 5 because of multiple root joints. I’m not sure why this error is happening because all of the joints are in a hierarchy. I even made sure to rename any joints with ‘root’ in the name and name the first joint in the hierarchy to ‘root’ so there would be no confusion with what the root joint is. It is not in a group either. Does anyone know how to solve this problem?