ADDITIONAL SYSTEM INFORMATION :
C:\Users\hwaite>ver

Microsoft Windows [Version 10.0.17763.1098]

A DESCRIPTION OF THE PROBLEM :
Pressing Alt-<key> to access menu imposes highlight that won't go away.

REGRESSION : Last worked in version 14

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Launch included application with VM params "-p <JavaFX home>\lib --add-modules javafx.controls"
2. Press Alt-A
3. Press Right-Arrow key

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Pressing Alt-A will highlight "Alpha" menu. Pressing Right-Arrow should unhighlight "Alpha" and highlight "Bravo".
ACTUAL -
After pressing Right-Arrow key, both "Alpha" and "Bravo" menus are highlighted.

---------- BEGIN SOURCE ----------
import java.util.stream.Collectors;
import java.util.stream.Stream;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuBar;
import javafx.scene.control.TableView;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

public class TestApp extends Application {
  public static void main(String[] pArgs) {launch(pArgs);}

  public void start(Stage pStage) {
    final BorderPane borderPane = new BorderPane();
    final MenuBar menuBar = new MenuBar();
    menuBar.getMenus().addAll(
      Stream.of("_Alpha", "_Bravo", "_Charlie", "").map(Menu::new).collect(
        Collectors.toList()
      )
    );
    borderPane.setTop(menuBar);
    borderPane.setCenter(new TableView<>());
    pStage.setScene(new Scene(borderPane));
    pStage.show();
  }
}
---------- END SOURCE ----------

FREQUENCY : always