When trying to load CSS from a file, change that file & reload, the changes don't get picked up.

Here is the test class:
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class ReloadCss extends Application
{
  String cssPath = ReloadCss.class.getResource("ReloadCss.css").toString();
  Scene scene;

  @Override
  public void start(Stage primaryStage) {
    Button btn = new Button("Reload CSS");
    btn.setOnAction(new EventHandler<ActionEvent>() {
      @Override
      public void handle(ActionEvent event) {
        scene.getStylesheets().clear();
        scene.getStylesheets().add(cssPath);
        System.out.println("Reloaded");
      }
    });

    StackPane root = new StackPane();
    root.getChildren().add(btn);

    scene = new Scene(root, 300, 250);
    scene.getStylesheets().add(cssPath);

    primaryStage.setTitle("Reload CSS Test");
    primaryStage.setScene(scene);
    primaryStage.show();
  }

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

And a .css file:
.root {
    -fx-font-size: 15px;
}

If the font size is changed between runs, it takes.
If the font size is changed & the button clicked, it doesn't take.
If scene.getStylesheets().add() adds a NEW stylesheet, that will work.