ADDITIONAL SYSTEM INFORMATION :
This bugs is not a regression but probably exists from a long time and is not OS specific, it's a bug in the TabPaneSkin implementation.

A DESCRIPTION OF THE PROBLEM :
When updating the tabs in TabPane and passing a new list but with already existing tabs (eventually in a different order), the order of the tabs may not match the requested order.







STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the provided JavaFx application source code and press the "Tabs 1 to 4" button. The UI will display Tab 3, Tab4, Tab 1, Tab 2 instead of ab 1, Tab 2, Tab 3, Tab 4

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
When pressing the button, the UI should display the tabs in this order: Tab 1, Tab 2, Tab 3 & Tab 4
ACTUAL -
When pressing the button, the UI actually displays the tabs in this order: Tab 3, Tab4, Tab 1, Tab 2

---------- BEGIN SOURCE ----------
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Tab;
import javafx.scene.control.TabPane;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class TabPaneBugApplication extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) {
        Tab tab1 = new Tab("Tab 1");
        Tab tab2 = new Tab("Tab 2");
        Tab tab3 = new Tab("Tab 3");
        Tab tab4 = new Tab("Tab 4");
        TabPane tabPane = new TabPane(tab1, tab2);

        Button button = new Button();
        button.setText("Tabs 1 to 4");
        button.setOnAction(event -> tabPane.getTabs().setAll(tab1, tab2, tab3, tab4));

        StackPane root = new StackPane();
        root.getChildren().setAll(tabPane, button);
        primaryStage.setScene(new Scene(root, 300, 250));
        primaryStage.show();
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
A workaround would be to never pass existing tabs again but always new tabs. This is however a develoment constraint that should'nt exist.

FREQUENCY : always