Cannot restart a QTimer timer after stopping it from a python script

I'm running a QWidget in python using an extended version of the following code:

class MyWidget(QWidget):
    def __init__(self):
        super().__init__()

        self.timer = QTimer(self)
        self.timer.timeout.connect(self.hello_world)
        self.timer.start(10000)

    
    def hello_world(self):
        print("Hello world")

class MyMainWindow(QMainWindow):
    def __init__(self, gates, **kwargs):
        super().__init__()
        self.widget = MyWidget()
        self.setCentralWidget(self.widget)

def _run_app(stop_event, widget_queue):
    _toggle_lock()
    app = QApplication(sys.argv)
    main_widget = InteractiveWindow()
    main_widget.show()
    widget_queue.put(main_widget.widget)
    print("GUI running")
 
    app.aboutToQuit.connect(_toggle_lock)
    while not stop_event.is_set():
        app.processEvents()
    app.quit()
    _toggle_lock(False)

def _toggle_lock(state=None):    
    global LOCK
    if state is None:
        LOCK = not LOCK
    else:
        LOCK = state    

def open_gui():
    if not LOCK:
        stop_event = threading.Event()
        widget_queue = queue.Queue()
        gui_thread = threading.Thread(target=_run_app, args=(stop_event, widget_queue), daemon=True)
        gui_thread.start()
        return gui_thread, stop_event, widget_queue.get()
    else:
        print("GUI is already running")

def close_gui(gui_thread, stop_event):
    if gui_thread.is_alive():
        stop_event.set()
        gui_thread.join()

Once I start up the widget from a python script using thread, stop, widget = open_gui(), the timer runs as expected printing "Hello world" every 10 seconds. I can also stop it from the notebook using widget.timer.stop() and it will stop printing. The problem comes when I try to restart the timer by calling widget.timer.start(10000), nothing happens.

I would like to find a way to restart the timer from outside its thread.