Incorrect selection if mouse is hovering over expanded menu:
To reproduce:
- expand the first menu and move the mouse to the 5-th item;
- press RIGHT arrow button;
- press LEFT arrow button;
The 5-th item (or other item under the mouse if it has been moved) will be selected unexpectedly. The first item should be selected.

Sample to check:
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class App extends Application {

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

    @Override
    public void start(Stage stage) throws Exception {
        MenuBar control = new MenuBar();
        for (int i = 0; i < 5; i++) {
            Menu m = new Menu("Menu " + String.valueOf(i + 1));
            for (int j = 0; j < 5; j++) {
                m.getItems().add(new MenuItem("Item " + String.valueOf(j + 1)));
            }
            control.getMenus().add(m);
        }
        Scene scene = new Scene(new HBox(control));
        stage.setScene(scene);
        stage.show();
    }
}