Mixamo -> Blender -> BJS issue

I just submitted a PR that will allow you to load assets with invalid skeleton values.

Various glTF fixes by bghgary · Pull Request #11996 · BabylonJS/Babylon.js (github.com)

You can also do this in the sandbox, but you have to load a model first before you can modify the settings. The settings will stick around until you refresh the page.