Rectangle in object-layer has wrong coordinates in game

Question

I extended the SuperKoalio LibGDX Example about an Tiled Object Layer in the Tiled Level-Editor and draw a rectangle on this layer. Now I would like to draw this rectangle in my game using the ShapeRenderer debugRenderer from the above SuperKoalio Example.

So, I changed the renderDebug method from example:

private void renderDebug () {
    Gdx.graphics.getGL20().glLineWidth(1.5F);

    // I think something is wrong with this:
    debugRenderer.setProjectionMatrix(camera.combined);

    debugRenderer.begin(ShapeType.Line);

    //Removed the rendering of the rectangles around ground and player

    // I added the object layer "objects" in the level1.tmx map
    // And this code:
    MapLayer objectLayer = map.getLayers().get("objects");
    debugRenderer.setColor(Color.RED);
    Rectangle rect;     
    for(MapObject mo : objectLayer.getObjects()) {
        rect = ((RectangleMapObject) mo).getRectangle();
        debugRenderer.rect(rect.x, rect.y, rect.width, rect.height);
    }

    debugRenderer.end();
}

Running this looks like: The rectangle is missing in game and I can't figure out why. Removing the setting of the ProjectionMatrix camera.combined makes the rectangle visible but it doesn't stick on the map and scrolls with the player. The position is a little wrong, too.

You can find my gist with modified example here.

How do I render this rectangle correctly? Thanks in advance!