I have a problem with a simple thing - I'm trying to impement dragging for actor, but I see strange effect - when I try to drag actor it starts blinking and change positions randomly. Here is a short video: <https://youtu.be/KpGujQ7KHc0>

Actor is simple:

```
public class Item extends Actor {
    private String id;
    private TextureRegion texture;

    public Item() {
        this.id = "passport";

        texture = PicturesData.getPicture(getId());
        setSize(texture.getRegionWidth(), texture.getRegionHeight());

        addListener(new DragListener() {
            @Override
            public boolean touchDown(InputEvent event, float x, float y, int pointer, int button) {
                return true;
            }

            @Override
            public void touchDragged(InputEvent event, float x, float y, int pointer) {
                Log.add("Dragged: " + x + ", " + y);
                setPosition(x, y);
            }
        });
    }

    public String getId() {
        return id;
    }

    @Override
    public void draw(Batch batch, float parentAlpha) {
        batch.draw(texture, getX(), getY());
    }
}

```

The screen is basic too:

```
public class GameScreen implements Screen {
    private Stage stage;

    public GameScreen() {
        stage = new Stage(new StretchViewport(800, 600));
        Gdx.input.setInputProcessor(stage);

        Item item = new Item();

        stage.addActor(item);
    }

    @Override
    public void show() {
    }

    @Override
    public void render(float delta) {
        Gdx.gl.glClearColor(0, 0, 0, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT | GL20.GL_DEPTH_BUFFER_BIT);

        stage.act(delta);
        stage.draw();
    }

    @Override
    public void resize(int width, int height) {

    }

    @Override
    public void pause() {

    }

    @Override
    public void resume() {

    }

    @Override
    public void hide() {

    }

    @Override
    public void dispose() {

    }
}

```

I have no idea why it's happening, could you please help me?