GLTF import fails on gltf.scene.clone()

[desert pewter]

In this example, everything is same about the model import except the "clone" button uses .clone().
http://jimm.horse/maze/marbletest.html

This seems to work but what's wrong with scene.clone()? https://gist.github.com/cdata/f2d7a6ccdec071839bc1954c32595e87#file-three-clone-gltf-js

[small cliff]

if your scene uses THREE.SkinnedMesh / armatures / bones, then .clone() cannot reconstruct the relationship between the mesh and its bones in the cloned scene.