To reproduce just click the menu. It will open and then it will close.

public class MenuItemTest extends Application {
    
    @Override
    public void start(Stage primaryStage) {
        
        Parent root = createScene();
        
        Scene scene = new Scene(root, 300, 250);
        
        primaryStage.setTitle(VersionInfo.getRuntimeVersion());
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

    private Parent createScene() {
        
        Menu menu = new Menu("Menu");
        
        for (int i = 0; i < 10; i++) {
            MenuItem menuItem = new MenuItem("Item - 0x1" + i);
            menu.getItems().add(menuItem);
        }
        
        MenuBar menuBar = new MenuBar();
        menuBar.getMenus().add(menu);
        
        HBox root = new HBox(5);
        root.getChildren().add(menuBar);
        
        return root;
    }
}