I’m running into the same issue on the import with the mocap recording. I can’t retarget in Unreal since it fails on the import due to the root track problem. I’ve tried to export the file with Blender (include root on the export) which didn’t solve the issue. Which brought me to motionBuilder. Do I just rename the bones in motionBuilder to match the naming convention of UE? There’s a slight difference in hierarchy (spine and neck). Any pointers on the workflow would be greatly appreciated.