Make QGraphicsItem not moveable in QGraphicsScene

I'm trying to make the qgraphicsitem not moveable. I tried setting the flag when its being clicked and tried setting it when the item is created etc. I can call flags(); and it shows that ItemIsMovable is not in the flags list yet it is still able to be moved. I have noticed when I pop up a modeless dialog in my mainwindow.cpp then go back to the mainwindow without closing the dialog and try to move an item it then recognizes the flag and I can't move the item until I close the dialog. I'm not sure why qgraphicsscene is ignoring the flag. Can anyone please explain how I can get this to work?

Here is some of my code stripped down to the relevant stuff.

Code:

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//GraphScene.h
class GraphScene : public QGraphicsScene
{
    private: 
        QGraphicsItem* x;
    protected:
        void mousePressEvent(QGraphicsSceneMouseEvent *event);
};
 
//GraphScene.cpp
void GraphScene::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
 
    x = qgraphicsitem_cast<QGraphicsItem*>(itemAt(event->scenePos(), QTransform()));
 
    if (x)
    {
        x->setFlag(QGraphicsItem::ItemIsMovable,false);
    }
 
    QGraphicsScene::mousePressEvent(event);
}
 
//y.h
class y : public QGraphicsObject
{
    protected:
        void mousePressEvent(QGraphicsSceneMouseEvent *event) Q_DECL_OVERRIDE;
};
 
//y.cpp
y::y()
{
    setFlags(ItemIsSelectable | ItemIsFocusable);
    this->setFlag(QGraphicsItem::ItemIsMovable,false);
    setAcceptHoverEvents(true);
}
void y::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
        QGraphicsItem::mousePressEvent(event);
        update();
}

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Please provide a minimum compilable example reproducing the problem.