JavaFX TableView sorting problem

HighscoreEntry.java

package meta;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectStreamException;
import java.io.Serializable;
import java.time.Duration;
import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.time.temporal.TemporalField;

import javafx.beans.property.SimpleIntegerProperty;
import javafx.beans.property.SimpleLongProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.beans.property.SimpleStringProperty;

public class HighscoreEntry {
	private SimpleStringProperty name;
	private SimpleIntegerProperty number, moves, fieldWidth, fieldHeight, mines;
	private SimpleObjectProperty<LocalDateTime> startTime;
	private SimpleObjectProperty<Duration> duration;
	
	public HighscoreEntry(int number, String name, LocalDateTime startTime, Duration duration,
                          int moves, int fieldWidth, int fieldHeight, int mines){
		this.number = new SimpleIntegerProperty (number);
		this.name = new SimpleStringProperty (name);
		this.startTime = new SimpleObjectProperty<LocalDateTime> (startTime);
		this.duration = new SimpleObjectProperty<Duration> (duration);
		this.moves = new SimpleIntegerProperty (moves);
		this.fieldWidth = new SimpleIntegerProperty (fieldWidth);
		this.fieldHeight = new SimpleIntegerProperty (fieldHeight);
		this.mines = new SimpleIntegerProperty (mines);
	}
	
	public HighscoreEntry(String name, LocalDateTime startTime, Duration duration,
            int moves, int fieldWidth, int fieldHeight, int mines){
		this(0, name, startTime, duration, moves, fieldWidth, fieldHeight, mines);
	}
	
	public HighscoreEntry(int number, String name, LocalDateTime startTime, Duration duration, int moves){
		this(number, name, startTime, duration, moves, 0, 0, 0);
	}
	
	public HighscoreEntry(String name, LocalDateTime startTime, Duration duration, int moves){
		this(0, name, startTime, duration, moves, 0, 0, 0);
	}
	
	public int getNumber(){
		return number.get();
	}
	
	public void setNumber(int number){
		this.number.setValue(number);
	}
	
	public String getName(){
		return name.get();
	}
	
	public void setName(String name){
		this.name.setValue(name);
	}
	
	public String getStartTime(){
		return startTime.getValue().format(DateTimeFormatter.ofPattern("dd.MM.yyyy HH:mm"));
	}
	
	public void setStartTime(String startTime){
		//TODO: Is it needed?
	}
	
	public String getDuration(){
		return String.format("%d:%02d.%03d", duration.getValue().getSeconds() / 60, (duration.getValue().getSeconds() % 60), duration.getValue().getNano() / 1000000);
	}
	
	public void setDuration(String duration){
		//TODO: Is it needed?
	}
	
	public int getMoves(){
		return moves.get();
	}
	
	public void setMoves(int moves){
		this.moves.setValue(moves);
	}
	
	public int getFieldWidth(){
		return fieldWidth.get();
	}
	
	public void setFieldWidth(int fieldWidth){
		this.fieldWidth.setValue(fieldWidth);
	}
	
	public int getFieldHeight(){
		return fieldHeight.get();
	}
	
	public void setFieldHeight(int fieldHeight){
		this.fieldHeight.setValue(fieldHeight);
	}
	
	public int getMines(){
		return mines.get();
	}
	
	public void setMines(int mines){
		this.mines.setValue(mines);
	}
}

HighscoreStage.java

package gui;

import java.time.LocalDateTime;

import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Tab;
import javafx.scene.control.TabPane;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.scene.text.Font;
import javafx.scene.text.Text;
import javafx.stage.Stage;
import meta.Data;
import meta.DataManager;
import meta.HighscoreEntry;
import meta.HighscoreList;

public class HighscoreStage extends Stage {
	
	private HighscoreTableView easyTable;
	private HighscoreTableView intermediateTable;
	private HighscoreTableView hardTable;
	private HighscoreTableView customTable;
	private Tab easyTab;
	private Tab intermediateTab;
	private Tab hardTab;
	private Tab customTab;

	public HighscoreStage(){
		super.setTitle("Highscore");
		super.setScene(createScene());
		super.showAndWait();
	}
	
	private Scene createScene(){
		Scene scene = new Scene(createRoot(), 500, 500);
		return scene;
	}
	
	private BorderPane createRoot(){
		BorderPane borderPane = new BorderPane();
//		borderPane.setPadding(new Insets(10, 10, 10, 10));
		
		borderPane.setCenter(createCenter());
		borderPane.setBottom(createBottom());
		
		return borderPane;
	}
	
	private GridPane createCenter(){
		GridPane gridPane = new GridPane();
		gridPane.setVgap(10d);
		gridPane.setHgap(10d);
		
		Text title = new Text("Highscore tables:");
		title.setFont(Font.font("Verdana", 26));
		gridPane.add(title, 0, 0);
		gridPane.setMargin(title, new Insets(10, 10, 10, 10));
		
		TabPane tabPane = createTabPane();
		gridPane.add(tabPane, 0, 1);
		gridPane.setHgrow(tabPane, Priority.ALWAYS);
		gridPane.setVgrow(tabPane, Priority.ALWAYS);
		
		return gridPane;
	}
	
	private TabPane createTabPane(){
		TabPane tabPane = new TabPane();
		
		easyTab = new Tab("Easy");
		intermediateTab = new Tab("Intermediate");
		hardTab = new Tab("Hard");
		customTab = new Tab("Custom");
		
		easyTab.setClosable(false);
		intermediateTab.setClosable(false);
		hardTab.setClosable(false);
		customTab.setClosable(false);
		
		tabPane.getTabs().addAll(easyTab, intermediateTab, hardTab, customTab);
		
		easyTable = new HighscoreTableView(false);
		intermediateTable = new HighscoreTableView(false);
		hardTable = new HighscoreTableView(false);
		customTable = new HighscoreTableView(true);
		
		easyTab.setContent(easyTable);
		intermediateTab.setContent(intermediateTable);
		hardTab.setContent(hardTable);
		customTab.setContent(customTable);
		
		loadData();
		return tabPane;
	}
	
	private void loadData(){
		easyTable.fillWithData(DataManager.getData().getHighscoresEasy());
		intermediateTable.fillWithData(DataManager.getData().getHighscoresIntermediate());
		hardTable.fillWithData(DataManager.getData().getHighscoresHard());
		customTable.fillWithData(DataManager.getData().getHighscoresCustom());
	}
	
	private HBox createBottom(){
		HBox hBox = new HBox();
		hBox.setAlignment(Pos.CENTER_RIGHT);
		hBox.setPadding(new Insets(10, 10, 10, 10));
		
		Button ok = new Button("OK");
		hBox.getChildren().add(ok);
		ok.setOnAction((event) -> {
			close();
		});
		
		Button reset = new Button("Reset Highscores");
		hBox.getChildren().add(reset);
		reset.setOnAction((event) -> {
			DataManager.getData().newHighscores();
			loadData();
		});
		
		return hBox;
	}
}

HighscoreTableView.java

/**
 * 
 */
package gui;

import javafx.scene.control.TableColumn;
import javafx.scene.control.TableColumn.SortType;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import meta.HighscoreEntry;
import meta.HighscoreList;

public class HighscoreTableView extends TableView<HighscoreEntry> {
	private HighscoreList list;
	private boolean isCustomHighscoreTable = false;
	private TableColumn<HighscoreEntry, Integer> number, moves, fieldWidth, fieldHeight, mines;
	private TableColumn<HighscoreEntry, String> name, startTime, duration;
	
	public HighscoreTableView(){
		this(null);
	}
	
	public HighscoreTableView(HighscoreList list, boolean isCustomHighscoreTable){
		super();
		this.list = list;
		this.isCustomHighscoreTable = isCustomHighscoreTable;
		this.initColumns();
	}
	
	public HighscoreTableView(HighscoreList list){
		this(list, false);
	}
	
	public HighscoreTableView(boolean isCustomHighscoreTable){
		this(null, isCustomHighscoreTable);
	}
	
	private void initColumns(){
		number = new TableColumn<HighscoreEntry, Integer>("#");
		name = new TableColumn<HighscoreEntry, String>("Name:");
		startTime = new TableColumn<HighscoreEntry, String>("Start time:");
		duration = new TableColumn<HighscoreEntry, String>("Duration:");
		moves = new TableColumn<HighscoreEntry, Integer>("Moves:");
		this.getColumns().addAll(number, name, startTime, duration, moves);
		if (this.isCustomHighscoreTable){
			fieldWidth = new TableColumn<HighscoreEntry, Integer>("Field width:");
			fieldHeight = new TableColumn<HighscoreEntry, Integer>("Field heighth:");
			mines = new TableColumn<HighscoreEntry, Integer> ("Mines:");
			this.getColumns().addAll(fieldWidth, fieldHeight, mines);
		}
		
		number.setCellValueFactory(new PropertyValueFactory<HighscoreEntry, Integer>("number"));
		name.setCellValueFactory(new PropertyValueFactory<HighscoreEntry, String>("name"));
		startTime.setCellValueFactory(new PropertyValueFactory<HighscoreEntry, String>("startTime"));
		duration.setCellValueFactory(new PropertyValueFactory<HighscoreEntry, String>("duration"));
		moves.setCellValueFactory(new PropertyValueFactory<HighscoreEntry, Integer>("moves"));
		if (this.isCustomHighscoreTable){
			fieldWidth.setCellValueFactory(new PropertyValueFactory<HighscoreEntry, Integer>("fieldWidth"));
			fieldHeight.setCellValueFactory(new PropertyValueFactory<HighscoreEntry, Integer>("fieldHeight"));
			mines.setCellValueFactory(new PropertyValueFactory<HighscoreEntry, Integer>("mines"));
		}
		
		duration.setSortType(TableColumn.SortType.DESCENDING);
		this.getSortOrder().add(duration);
		duration.setSortable(true);
		this.sort();
	}
	
	public void fillWithData(){
//		if (list == null){}//TODO: Fehlermeldung!
//		else {
//			for (HighscoreEntry i : list){
//				number.cellValueFactoryProperty().set
//			}
//		}
		this.setItems(list.getObservableList());
	}
	
	public void fillWithData(HighscoreList list){
		this.list = list;
		fillWithData();
	}
}

That's my gist, I accidently created it without being logged in.