To reproduce simply run the app and click at the text field.


public void start(Stage stage) {

        HBox root = new HBox(20d);

        TextField textField = new TextField();
        root.getChildren().add(textField);
        
        root.getChildren().add(new Button("Button"));
        
        Scene scene = new Scene(root, 300, 250);

        stage.setScene(scene);
        stage.setTitle(System.getProperty("java.runtime.version") + "; " + System.getProperty("javafx.runtime.version"));
        stage.show();
    }