ADDITIONAL SYSTEM INFORMATION :
CentOS 7, OpenJDK 18

A DESCRIPTION OF THE PROBLEM :
After upgrading from OpenJFX 20 to 21 I have noticed that opening any dialog, like for example an Alert, will cause the main stage/window to snap out of its maximized state, if it has been maximized. I have only observed this on Linux/CentOS, on Windows 10 the behaviour is as expected.

I can reliably reproduce this issue with the given test program, which just opens a window and shows an Alert when pressing a button.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
- Run the example code
- Maximize the window
- Press the button to show an Alert

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The Alert should show up and the window should remain unaffected
ACTUAL -
The Alert shows up but the window is no longer maximized

---------- BEGIN SOURCE ----------
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

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

    @Override
    public void start(Stage primaryStage) {
        ToggleButton buttonAbout = new ToggleButton("Show Dialog");
        buttonAbout.setOnAction(event -> {
            Alert alert = new Alert(Alert.AlertType.INFORMATION);
            alert.show();
        });

        HBox hbox = new HBox();
        hbox.getChildren().add(buttonAbout);

        Scene scene = new Scene(hbox);
        primaryStage.setScene(scene);
        primaryStage.setTitle("Main Window");
        primaryStage.show();
    }
}
---------- END SOURCE ----------

FREQUENCY : always