Updating MediaPlayer properties on a background thread causes exceptions to be thrown when those properties are bound to scene graph nodes. The following example program demonstrates the bug:

public class CurrentTimeUpdatedOffAppThread extends Application {

  public static void main(String[] args) {
    launch(args);
  }
  
  @Override
  public void start(Stage primaryStage) {
    System.out.println("JavaFX version: "+VersionInfo.getRuntimeVersion());
    Media m = new Media("http://traffic.libsyn.com/dickwall/JavaPosse373.mp3");
    MediaPlayer mp = new MediaPlayer(m);

    Label label = new Label();
    label.textProperty().bind(Bindings.convert(mp.currentTimeProperty()));
    
    final Scene scene = new Scene(new Group(label), 200, 200);
    
    primaryStage.setScene(scene);
    primaryStage.setTitle("CurrentTime Bug");
    primaryStage.show();
    
    mp.play();
  }
}

After a few seconds, the media will begin to play and an exception will be thrown.