MessagingCenter catching message twice

Question

I am trying to use the messaging center to send a simple string through the messaging center. And it works. But for some reason, despit only sending one message, it's caught twice.

Here's the sending page:

protected override void OnAppearing()
    {
        base.OnAppearing();

        MessagingCenter.Subscribe<App, string>(this, "Barcode", (sender, arg) => {
            Device.BeginInvokeOnMainThread(() =>
            {
                HandleReadLabel(arg);
            });
        });

        viewModel.LoadItemsCommand.Execute(null);
    }

    protected override void OnDisappearing()
    {
        base.OnDisappearing();

        MessagingCenter.Unsubscribe<App, string>(this, "Barcode");
    }

    public async Task<bool> HandleReadLabel(string labelText)
    {

        await Navigation.PopAsync();
        MessagingCenter.Send<App, string>((App)Application.Current, "Trolley", labelText);
        return true;
    }
    private async void btnTest_Clicked(object sender, EventArgs e)
    {
        string LabelTrolley = (sender as Button).Text;
        await Navigation.PopAsync();
        MessagingCenter.Send<App, string>((App)Application.Current, "Trolley", LabelTrolley);


    }

two ways of sending that message: click on a button, or use the barcode scanner that is linked to the device (I have no problem with that subsciption, but I compared the two and couldn't find the issue)

Then the receiving page:

public Inv2Page(bool isMoveGoods)
    {
        InitializeComponent();
        
        if (isMoveGoods)
            viewModel = new Inv2ViewModel(ItemsListView, ItemsListViewTransfer, SelectionBinBoxView, "Move Goods");
        else
            viewModel = new Inv2ViewModel();

        viewModel.LabelBin = "SCAN";
        viewModel.IsMoveGoods = isMoveGoods;
        BindingContext = viewModel;


        MessagingCenter.Unsubscribe<App, string>(this, "Trolley");
        MessagingCenter.Subscribe<App, string>(this, "Trolley", (sender, arg) => {
            Device.BeginInvokeOnMainThread(() =>
            {
                HandleReadLabel(arg);
                viewModel.LoadItemsCommand.Execute(null);
            });
        });
    }

With no unsubsciption on disappearing.

The subscribed page is always behind the subsciption, and when I get the answer I want from the subscription, it sends the message back and disappear. Then it triggers the result twice.