Rendering 3D Objects while using box2Dlights causes glitches

Hi and thanks for this cool piece of software 👍
Now my Problem: Everything works fine, but when I start rendering 3D objects in my world, graphic glitches start approaching on them. In the example picture, you can see the effect on an green cube without any texture.

• With box2Dlight:
  

• Without box2Dlight:
  

In my render-loop, the source looks something like this:

init() {
        this.rayHandler = rayHandler;
        rayHandler.setCulling(true);
        rayHandler.setAmbientLight(0.1f, 0.1f, 0.1f, 0.5f);
        rayHandler.setAmbientLight(0.8f, 0.8f, 0.8f, 0.5f);
        rayHandler.setBlurNum(3);

        environment = new Environment();
        environment.set(new ColorAttribute(ColorAttribute.AmbientLight, 0.4f, 0.4f, 0.4f, 1f));
        environment.add(new DirectionalLight().set(0.8f, 0.8f, 0.8f, -1f, -0.8f, -0.2f));
}
render(float deltatime){
       //...
       // (render 2D/Sprites)
       // (render 3D objects)
       //...

       rayHandler.setCombinedMatrix(cam);
       rayHandler.updateAndRender();
}

How can I avoid these effects?

Start with the supplied init and render loop, reproducing the green cube glitches with box2dlights enabled and disabled. Compare the 2D, 3D, and rayHandler rendering order and state, then verify that the cube renders without artifacts while the lighting remains active.