The first sub model in any model is named__ root__ 0, does this have any effect?
this is how gltf/glb assets are structured, I personally do not like this either and I know others here feel the same, so we unparent the siblings and delete this root node.
The root node is used to convert between GLTF’s native right-handed system and Babylon’s left-handed system without touching the transformations on the model’s actual nodes 
You can remove the root but be aware this will change the transformation on your model.