Incorrect selection while navigating between menu items. To reproduce:
- expand drop down menu window by mouse or DOWN arrow key;
- move the selection pointer to the second item by pushing DOWN key;
- collapse menu by ESC key or select the second item;
- expand drop down menu window by mouse or DOWN arrow key;
- press DOWN arrow key
Third item will be selected. It seems that the the last selection state is restored.

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 {
        MenuButton control = new MenuButton("MenuButton");
        for (int i = 0; i < 5; i++) {
            control.getItems().add(new MenuItem("Item " + String.valueOf(i + 1)));
        }
        Scene scene = new Scene(new HBox(control));
        stage.setScene(scene);
        stage.show();
    }
}