When I use SubScene my 3D models start to glitch. Any ideas why?

Question

I am building an application that has 2 SubScenes, one for GUI and one for displaying 3D models (in my case OBJ).

For the import of the OBJ file I use the ObjModelImporterJFX library by InteractiveMesh.

Like the title says and as seen in this picture the models start to glitch when they are handled by a SubScene. It seems like some covered parts that should not be visible are rendered like they were. Just for comparison this is how it looks normally, when the models are handled direcly by the scene.

Here is my code:

public class Main extends Application{

    @Override
    public void start(Stage stage) throws Exception{

        Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));

        PerspectiveCamera camera = new PerspectiveCamera(true);

        Group model = loadOBJ("course.obj");
        Group course = new Group(model);

        BorderPane borderPane = new BorderPane();

        Pane pane1 = new Pane(course);
        Pane pane2 = new Pane(root);

        SubScene subScene1 = new SubScene(pane1, 1000, 720);
        subScene1.setCamera(camera);

        SubScene subScene2 = new SubScene(pane2,500,500);

        borderPane.setLeft(subScene1);
        borderPane.setRight(subScene2);

        Scene scene = new Scene(borderPane, 1280,720, true);

        stage.setScene(scene);
        stage.show();
    }


    private Group loadOBJ(String fileName){

        URL url = getClass().getResource(fileName);

        Group modelRoot = new Group();

        ObjModelImporter importer = new ObjModelImporter();
        importer.read(url);

        for (MeshView view : importer.getImport()){
            modelRoot.getChildren().add(view);
        }

        return modelRoot;
    }


    public static void main(String[] args){
        launch(args);
    }
}

I hope that someone has an idea why this is. Thanks in advance :)

UPDATE: To fix this enable depthBuffer by changing the constructor of the SubScene from

SubScene subScene1 = new SubScene(pane1, 1000, 720);

to

SubScene subScene1 = new SubScene(pane1, 1000, 720, true, null);