A DESCRIPTION OF THE PROBLEM :
I have a MenuButton containing several MenuItems and one CustomMenuItem containing a Textfield. The TextField has an EventHandler added (not set), the other MenuItems also have an EventHandler.
When I select the TextField and hit Enter, the TextField's EventHandler gets triggered, BUT ALSO the one of the item above.
This behaviour does NOT occur, if I use setOnAction(.) to add the TextField's Handler instead of (or in addition to) addEventHandler(.).

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
In the code below, a GUI containing just a button gets started.
Click inside the Textfield to place the cursor, then hit enter.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
TextField's listener gets triggered and prints "ADD: <Text you typed> ..."
ACTUAL -
TextField's listener gets triggered and prints "ADD: <Text you typed> ..."
AND above Button's listener gets triggered and prints "World! ...". This should only happen, if I click "World".

---------- BEGIN SOURCE ----------
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.scene.Scene;
import javafx.scene.control.CustomMenuItem;
import javafx.scene.control.MenuButton;
import javafx.scene.control.MenuItem;
import javafx.scene.control.TextField;
import javafx.stage.Stage;

public class CustomMenuTest extends Application {
    @Override
    public void start(Stage primaryStage) throws Exception {

        MenuButton menu = new MenuButton("Fancy Menu...");

        MenuItem hello = new MenuItem("Hello");
        hello.setOnAction(event -> System.out.println("Hello | " + event.getSource()));

        MenuItem world = new MenuItem("World!");
        world.setOnAction(event -> System.out.println("World! | " + event.getSource()));

        /*
        Set the cursor into the TextField, maybe type something, and hit enter.
        --> Expected: "ADD: <Text you typed> ..."
        --> Actual: "ADD: <Text you typed> ..." AND "World! ..." - so the button above gets triggered as well.
        If I activate listener (II) or (III), everything works fine - even the empty action in (III) does is job, but this is ugly...
        (And I can't use (II), because I need (I).
         */
        TextField textField = new TextField();
        /*   I */ textField.addEventHandler(ActionEvent.ACTION,
                                  event -> System.out.println("ADD: " + textField.getText() + " | " + event.getSource()));
        /*  II */ // textField.setOnAction(event -> System.out.println("SET: " + textField.getText() + " | " + event.getSource()));
        /* III */ // textField.setOnAction(__ -> {/* do nothing */});

        CustomMenuItem custom = new CustomMenuItem(textField, false);

        menu.getItems().addAll(hello, world, custom);

        primaryStage.setScene(new Scene(menu));
        primaryStage.show();
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
textField.setOnAction(__ -> {/* do nothing */});

this way, everything works fine and only "ADD: ..." gets printed.

FREQUENCY : always