Normals UV bug?

I am having problems with a scene exported from Blender 2.8 using gltf2.
The scene loads but some normal of horizontal faces are inverted by BabylonJS. If I flip a particular horizontal face and re-export the Babylon still shows the normal inverted (no effect flipping in blender). Sandbox shows fine but it seems that faces get material applied in both sides:

The following link has my test code and the Blender file:

Thanks in advance,

ping @bghgary in case he is aware for the blender exporter ?

False alarm… my HemisphericLight was perpendicular to all horizontal faces in opposite side. The following change solved it:

var light = new BABYLON.HemisphericLight(“HemiLight”, new BABYLON.Vector3(-0.5, -1, -0.5), scene);