Qt jambi 4.7.1 - QGraphicsItem return to its initial position on second drag

I use Qt jambi 4.7.1 for my project. I have made a abstract class named Component who extends QGraphicsRectItem. I've set my Component flags with the purpose to move it into a same QGraphicsScene.

public abstract class Component extends QGraphicsRectItem{

 public Signal1<QPoint>  componentMoved = new Signal1<QPoint>();
 private int id;
 private int nextId;
 private List<Route> routes = new ArrayList<Route>();
 protected QPixmap image;
 protected static QSizeF size = new QSizeF(100, 100);    

public Component(int pointX1, int pointY1, int id) {

    super(new QRectF(new QPointF(pointX1,pointY1),size));       
    this.id = id;


    //this.setFlag(GraphicsItemFlag.ItemIsSelectable, true);
    this.setFlag(GraphicsItemFlag.ItemIsMovable,true);

    this.setFlag(GraphicsItemFlag.ItemSendsGeometryChanges, true);      
    this.setCacheMode(CacheMode.DeviceCoordinateCache,new QSize(1024,1024));

}

public void drawComponent(){
    new QGraphicsPixmapItem(image.scaled(size.toSize()), this);     
}   

@Override
public void mousePressEvent(QGraphicsSceneMouseEvent e){
    this.setTransformOriginPoint(e.scenePos());
}

@Override
public Object itemChange(GraphicsItemChange change, Object value){
    switch (change) {
    case ItemPositionHasChanged:

        QPointF currentPos = this.scenePos();
        componentMoved.emit(currentPos.toPoint());              
        break;
    default:
        break;
    }       
    return super.itemChange(change, value);
}

public int getId(){
    return id;
}

public int getNextId(){
    return nextId;
}   

public QPixmap getImage(){
    return image;
}

public List<Route> getRoutes(){
    return routes;
}

public QSizeF getSize(){
    return size;
}

public void addRoute(Component nextComponent){
    //routes.add(new Route(this, nextComponent));
}

So it work, now I can move my Component in my scene with a mouse click. But, I have a bug when I move my Component it always return to its initial position before each drag. I'm sure it's just a simple thing but I've searched a long time on internet and I've found nothing.

Sorry for my bad english! :P

The bug is not occurred anymore for unknown reason! I think my components didn't update their position correctly to the graphicsscene. So I probably modify some codes in relation with the display of my components and resolve the bug by accident. If I'll find what exactly cause this bug, I will update this post!