When a stage is maximized -> iconified -> restored, the iconifiedProperty of the stage won't get properly updated. The test below demonstrates the behavior - when the stage is iconified newValue is true, when the stage is restored the listener does not receive any event.The issue does not occur if the stage is not maximized.

public class IconifiedPropertyTest extends Application
{

  public static void main(String[] args)
  {
    Application.launch(IconifiedPropertyTest.class, args);
  }

  @Override
  public void start(Stage stage)
  {
    stage.iconifiedProperty().addListener(new ChangeListener<Boolean>()
    {
      @Override
      public void changed(ObservableValue<? extends Boolean> observable, Boolean oldValue, Boolean newValue)
      {
        System.err.println("isIconified: " + newValue);
      }
    });
    
    BorderPane root = new BorderPane();
    Scene scene = new Scene(root, 800, 600);
    stage.setScene(scene);
    //iconifiedProperty works fine if window is not maximized
    stage.setMaximized(true);
    stage.show();
  }
}