Program: 36609
Project: 36609
Buggy source:
@Override public void init(){
  balance=new Balancer();
  soundGrid.add(balance,1,1);
  balance.setPrefSize(50,20);
  balance.setMax(PLAYBACK.getBalanceMax());
  balance.setMin(PLAYBACK.getBalanceMin());
  balance.balanceProperty().bindBidirectional(PLAYBACK.balanceProperty());
  volume.setMin(PLAYBACK.getVolumeMin());
  volume.setMax(PLAYBACK.getVolumeMax());
  volume.setValue(PLAYBACK.getVolume());
  volume.valueProperty().bindBidirectional(PLAYBACK.volumeProperty());
  seeker.bindTime(PLAYBACK.totalTimeProperty(),PLAYBACK.currentTimeProperty());
  entireArea.getChildren().add(seeker);
  AnchorPane.setBottomAnchor(seeker,0.0);
  AnchorPane.setLeftAnchor(seeker,0.0);
  AnchorPane.setRightAnchor(seeker,0.0);
  seeker.setChapterSnapDistance(GUI.snapDistance);
  p1.setOnMouseClicked(e -> rewind());
  f2.setOnMouseClicked(e -> previous());
  f3.setOnMouseClicked(e -> play_pause());
  f4.setOnMouseClicked(e -> next());
  f5.setOnMouseClicked(e -> forward());
  f6.setOnMouseClicked(e -> stop());
  playButtons.getChildren().setAll(p1,f2,f3,f4,f5,f6);
  Tooltip.install(addB,new Tooltip("String_Node_Str"));
  addB.setOnMouseClicked(e -> {
    if (e.getButton() == MouseButton.PRIMARY)     PlaylistManager.addOrEnqueueFiles(true);
 else     PlaylistManager.addOrEnqueueFolder(true);
  }
);
  entireArea.getChildren().add(addB);
  AnchorPane.setTopAnchor(addB,5d);
  AnchorPane.setLeftAnchor(addB,5d);
  loopB.setOnMouseClicked(e -> PLAYBACK.toggleLoopMode());
  loopB.setScaleX(1.3);
  infoBox.getChildren().add(1,loopB);
  muteB.setOnMouseClicked(e -> cycleMute());
  soundGrid.add(muteB,0,0);
  playingItemMonitoring=Player.playingtem.subscribeToUpdates(this::playingItemChanged);
  playingItemChanged(Player.playingtem.get());
  PLAYBACK.statusProperty().addListener(statusListener);
  statusChanged(PLAYBACK.getStatus());
  PLAYBACK.loopModeProperty().addListener(loopModeListener);
  loopModeChanged(PLAYBACK.getLoopMode());
  PLAYBACK.muteProperty().addListener(muteListener);
  muteChanged(PLAYBACK.getMute(),volume.getValue());
  PLAYBACK.totalTimeProperty().addListener(totalTimeListener);
  PLAYBACK.realTimeProperty().addListener(realTimeListener);
  PLAYBACK.currentTimeProperty().addListener(currTimeListener);
  currTimeListener.invalidated(null);
  ChangeListener<Number> volumeListener=(o,ov,nv) -> muteChanged(PLAYBACK.isMute(),nv.doubleValue());
  volume.valueProperty().addListener(volumeListener);
  entireArea.setOnDragOver(DragUtil.audioDragAccepthandler);
  entireArea.setOnDragDropped(e -> {
    if (DragUtil.hasAudio(e.getDragboard())) {
      List<Item> items=DragUtil.getAudioItems(e);
      e.setDropCompleted(true);
      e.consume();
      if (playDropped) {
        PlaylistManager.playPlaylist(new Playlist(items.stream().map(Item::getURI),true));
      }
 else {
        PlaylistManager.addItems(items);
      }
    }
  }
);
}

Fixed version (ground truth):
@Override public void init(){
  balance=new Balancer();
  soundGrid.add(balance,1,1);
  balance.setPrefSize(50,20);
  balance.setMax(PLAYBACK.getBalanceMax());
  balance.setMin(PLAYBACK.getBalanceMin());
  balance.balanceProperty().bindBidirectional(PLAYBACK.balanceProperty());
  volume.setMin(PLAYBACK.getVolumeMin());
  volume.setMax(PLAYBACK.getVolumeMax());
  volume.setValue(PLAYBACK.getVolume());
  volume.valueProperty().bindBidirectional(PLAYBACK.volumeProperty());
  seeker.bindTime(PLAYBACK.totalTimeProperty(),PLAYBACK.currentTimeProperty());
  entireArea.getChildren().add(seeker);
  AnchorPane.setBottomAnchor(seeker,0.0);
  AnchorPane.setLeftAnchor(seeker,0.0);
  AnchorPane.setRightAnchor(seeker,0.0);
  d1=maintain(GUI.snapDistance,d -> d,seeker.chapterSnapDistance);
  p1.setOnMouseClicked(e -> rewind());
  f2.setOnMouseClicked(e -> previous());
  f3.setOnMouseClicked(e -> play_pause());
  f4.setOnMouseClicked(e -> next());
  f5.setOnMouseClicked(e -> forward());
  f6.setOnMouseClicked(e -> stop());
  playButtons.getChildren().setAll(p1,f2,f3,f4,f5,f6);
  Tooltip.install(addB,new Tooltip("String_Node_Str"));
  addB.setOnMouseClicked(e -> {
    if (e.getButton() == MouseButton.PRIMARY)     PlaylistManager.addOrEnqueueFiles(true);
 else     PlaylistManager.addOrEnqueueFolder(true);
  }
);
  entireArea.getChildren().add(addB);
  AnchorPane.setTopAnchor(addB,5d);
  AnchorPane.setLeftAnchor(addB,5d);
  loopB.setOnMouseClicked(e -> PLAYBACK.toggleLoopMode());
  loopB.setScaleX(1.3);
  infoBox.getChildren().add(1,loopB);
  muteB.setOnMouseClicked(e -> cycleMute());
  soundGrid.add(muteB,0,0);
  playingItemMonitoring=Player.playingtem.subscribeToUpdates(this::playingItemChanged);
  playingItemChanged(Player.playingtem.get());
  PLAYBACK.statusProperty().addListener(statusListener);
  statusChanged(PLAYBACK.getStatus());
  PLAYBACK.loopModeProperty().addListener(loopModeListener);
  loopModeChanged(PLAYBACK.getLoopMode());
  PLAYBACK.muteProperty().addListener(muteListener);
  muteChanged(PLAYBACK.getMute(),volume.getValue());
  PLAYBACK.totalTimeProperty().addListener(totalTimeListener);
  PLAYBACK.realTimeProperty().addListener(realTimeListener);
  PLAYBACK.currentTimeProperty().addListener(currTimeListener);
  currTimeListener.invalidated(null);
  ChangeListener<Number> volumeListener=(o,ov,nv) -> muteChanged(PLAYBACK.isMute(),nv.doubleValue());
  volume.valueProperty().addListener(volumeListener);
  entireArea.setOnDragOver(DragUtil.audioDragAccepthandler);
  entireArea.setOnDragDropped(e -> {
    if (DragUtil.hasAudio(e.getDragboard())) {
      List<Item> items=DragUtil.getAudioItems(e);
      e.setDropCompleted(true);
      e.consume();
      if (playDropped) {
        PlaylistManager.playPlaylist(new Playlist(items.stream().map(Item::getURI),true));
      }
 else {
        PlaylistManager.addItems(items);
      }
    }
  }
);
}