Run this code.
Click on any Sphere. On console you will see value of Node.computeAreaInScreen().
Then press '2', to translate Spheres. Click on same Sphere again. Value is changed. Ok.
Then press '4', to translate Group, contans Spheres. Click on same Sphere, and you will see that Value on console is not changed. This is the problem.

If you will delete line 55 (adding light), you will see that in this case Lod works correct.