Program: 36544
Project: 36544
Buggy source:
@Override public void init(){
  data_out=outputs.create(widget.id,"String_Node_Str",Metadata.class,EMPTY);
  d(Player.onItemRefresh(refreshed -> refreshed.ifHasE(data,this::read)));
  cover.getPane().setDisable(true);
  cover.setBackgroundVisible(false);
  cover.setBorderToImage(false);
  cover.onFileDropped=fut_file -> App.actionPane.show(File.class,fut_file,new SlowAction<>("String_Node_Str","String_Node_Str" + "String_Node_Str" + "String_Node_Str"+ "String_Node_Str"+ data.getLocation().getPath(),FontAwesomeIcon.PASTE,f -> setAsCover(f,true)),new SlowAction<>("String_Node_Str","String_Node_Str" + "String_Node_Str" + data.getLocation().getPath(),FontAwesomeIcon.COPY,f -> setAsCover(f,false)),new SlowAction<>("String_Node_Str","String_Node_Str" + "String_Node_Str",FontAwesomeIcon.TAG,f -> tagAsCover(f,false)),new SlowAction<>("String_Node_Str","String_Node_Str" + "String_Node_Str" + "String_Node_Str",FontAwesomeIcon.TAGS,f -> tagAsCover(f,true)));
  layAnchor(root,layout,0d);
  layout.setMinContentSize(200,120);
  layout.setGap(5);
  tiles.setPadding(new Insets(5));
  tiles.setAlignment(TOP_LEFT);
  tiles.setTileAlignment(CENTER_LEFT);
  rating.setGraphic(rater);
  rating.setContentDisplay(ContentDisplay.RIGHT);
  rater.icons.bind(App.maxRating);
  rater.partialRating.bind(App.partialRating);
  rater.updateOnHover.bind(App.hoverRating);
  rater.editable.bind(App.allowRatingChange);
  rater.setOnRatingChanged(r -> MetadataWriter.useToRate(data,r));
  root.setOnDragOver(DragUtil.audioDragAccepthandler);
  root.setOnDragDropped(e -> {
    if (DragUtil.hasAudio(e.getDragboard())) {
      DragUtil.getSongs(e).use(items -> items.findFirst().ifPresent(this::read),FX).run();
      e.setDropCompleted(true);
      e.consume();
    }
  }
);
  installDragSignalPane(root,DETAILS,"String_Node_Str");
}

Fixed version (ground truth):
@Override public void init(){
  data_out=outputs.create(widget.id,"String_Node_Str",Metadata.class,EMPTY);
  d(Player.onItemRefresh(refreshed -> refreshed.ifHasE(data,this::read)));
  cover.getPane().setDisable(true);
  cover.setBackgroundVisible(false);
  cover.setBorderToImage(false);
  cover.onFileDropped=fut_file -> App.actionPane.show(File.class,fut_file,new SlowAction<>("String_Node_Str","String_Node_Str" + "String_Node_Str" + "String_Node_Str"+ "String_Node_Str"+ data.getLocation().getPath(),FontAwesomeIcon.PASTE,f -> setAsCover(f,true)),new SlowAction<>("String_Node_Str","String_Node_Str" + "String_Node_Str" + data.getLocation().getPath(),FontAwesomeIcon.COPY,f -> setAsCover(f,false)),new SlowAction<>("String_Node_Str","String_Node_Str" + "String_Node_Str",FontAwesomeIcon.TAG,f -> tagAsCover(f,false)),new SlowAction<>("String_Node_Str","String_Node_Str" + "String_Node_Str" + "String_Node_Str",FontAwesomeIcon.TAGS,f -> tagAsCover(f,true)));
  layAnchor(root,layout,0d);
  layout.setMinContentSize(200,120);
  layout.setGap(5);
  tiles.setPadding(new Insets(5));
  tiles.setAlignment(TOP_LEFT);
  tiles.setTileAlignment(CENTER_LEFT);
  rating.setGraphic(rater);
  rating.setContentDisplay(ContentDisplay.RIGHT);
  rater.icons.bind(App.maxRating);
  rater.partialRating.bind(App.partialRating);
  rater.updateOnHover.bind(App.hoverRating);
  rater.editable.bind(App.allowRatingChange);
  rater.setOnRatingChanged(r -> MetadataWriter.useToRate(data,r));
  root.setOnDragOver(DragUtil.audioDragAccepthandler);
  root.setOnDragDropped(e -> {
    if (DragUtil.hasAudio(e.getDragboard())) {
      DragUtil.getSongs(e).use(items -> items.findFirst().ifPresent(this::read),FX).run();
      e.setDropCompleted(true);
      e.consume();
    }
  }
);
  installDragSignalPane(root,DETAILS,"String_Node_Str",DragUtil::hasAudio);
}