usercontrol loaded event doesn't fire, missing loaded event


When there are many items in listbox, the listbox item template loaded event doesn't fire.

I have made a template for the ItemTemplate property of ListBox:
        <ListBox x:Name="lb" Grid.Row="1">
                    <StackPanel Orientation="Vertical"/>
                    <local:ListBoxItemTemplate />
I have handled the loaded event of local:ListBoxItemTemplate :
        void ListBoxItemTemplate_Loaded(object sender, RoutedEventArgs e)
But, on my side, when the items number is over 5000, there are some loaded event doesn't fire.
When I increase the number to 100000, there is no loaded event any more.
Is this a bug? Or I missed any thing?

I have attached a completely sample here, you can change the amount in the ListBoxDataViewModel.cs file.

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