XAML to reproduce bug

Window

<Window x:Class="DefaultsExample.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:dd="clr-namespace:GongSolutions.Wpf.DragDrop;assembly=GongSolutions.Wpf.DragDrop"
        xmlns:local="clr-namespace:DefaultsExample"
        Title="Gong Solutions Drag'n'Drop: Defaults Example"
        Height="500"
        Width="800">

    <Window.Resources>
        <DataTemplate x:Key="DragAdorner">
            <Border Background="Silver"
              BorderBrush="Gray"
              BorderThickness="1"
              CornerRadius="2"
              Margin="1">
                <StackPanel Orientation="Horizontal">
                    <Image Source="/icon.png"
                 Width="16"
                 Margin="0,0,2,0"
                 VerticalAlignment="Center" />
                    <TextBlock Text="{Binding}"
                     Margin="0,0,2,0"
                     VerticalAlignment="Center" />
                </StackPanel>
            </Border>
        </DataTemplate>

        <CollectionViewSource x:Key="GroupedCollectionViewSource"
                          Source="{Binding GroupedCollection}">
            <CollectionViewSource.GroupDescriptions>
                <PropertyGroupDescription PropertyName="Group" />
            </CollectionViewSource.GroupDescriptions>
        </CollectionViewSource>
    </Window.Resources>

    <Window.DataContext>
        <local:Data />
    </Window.DataContext>

    <StackPanel Orientation="Horizontal">
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition />
                <ColumnDefinition />
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition />
            </Grid.RowDefinitions>

            <TextBlock Grid.Row="0"
                   Grid.ColumnSpan="2"
                   Margin="0,8,0,8"
                   TextWrapping="Wrap">
                    Demonstrates the default behaviour with two ListBoxes bound to two collections of the same type.
            </TextBlock>

            <ListBox Grid.Column="0" BorderThickness="1"
                 Grid.Row="1"
                 ItemsSource="{Binding Collection1}"
                 SelectionMode="Extended"
                 dd:DragDrop.IsDragSource="True"
                 dd:DragDrop.IsDropTarget="True"
                 dd:DragDrop.UseDefaultEffectDataTemplate="True"
                 dd:DragDrop.DragAdornerTemplate="{StaticResource DragAdorner}" />
            <ListBox Grid.Column="1"
                 Grid.Row="1"
                 ItemsSource="{Binding Collection2}"
                 dd:DragDrop.IsDragSource="True"
                 dd:DragDrop.IsDropTarget="True"
                 dd:DragDrop.DragAdornerTemplate="{StaticResource DragAdorner}" />
        </Grid>
    </StackPanel>
</Window>