Extra space in ListBox with VirtualizingStackPanel

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C#

WPF

I am using a ListBox with ItemsPanel set to VirtualizingStackPanel.

<ListBox ItemsSource="{Binding Items}"
                 ScrollViewer.VerticalScrollBarVisibility="Visible">
            <ItemsControl.ItemsPanel>
                <ItemsPanelTemplate>
                    <VirtualizingStackPanel Orientation="Horizontal"
                                        VirtualizationMode="Recycling"
                                        HorizontalAlignment="Stretch"
                                        VerticalAlignment="Top"
                                        />
                </ItemsPanelTemplate>
            </ItemsControl.ItemsPanel>

            <ItemsControl.ItemTemplate>
                <DataTemplate>

                    <DataGrid 
                          VerticalAlignment="Top"
                          HeadersVisibility="None"
                          ItemsSource="{Binding Distances}">

                        <DataGrid.Columns>
                            <DataGridTemplateColumn IsReadOnly="True" Width="100">
                                <DataGridTemplateColumn.CellTemplate>
                                    <DataTemplate>
                                        <TextBlock Text="{Binding FactDistance}"/>
                                    </DataTemplate>
                                </DataGridTemplateColumn.CellTemplate>
                            </DataGridTemplateColumn>

                            <DataGridTemplateColumn Width="100">
                                <DataGridTemplateColumn.CellTemplate>
                                    <DataTemplate>
                                        <TextBlock Text="{Binding NormDistanceValue}"
                                                   VerticalAlignment="Stretch"
                                                   HorizontalAlignment="Stretch"
                                                   TextAlignment="Center"/>
                                    </DataTemplate>
                                </DataGridTemplateColumn.CellTemplate>
                            </DataGridTemplateColumn>

                              <DataGridTemplateColumn Width="100">
                                <DataGridTemplateColumn.CellTemplate>
                                    <DataTemplate>
                                        <TextBlock Text="{Binding NormLiterature}"
                                                   VerticalAlignment="Stretch"
                                                   HorizontalAlignment="Stretch"
                                                   TextAlignment="Center"/>
                                    </DataTemplate>
                                </DataGridTemplateColumn.CellTemplate>
                            </DataGridTemplateColumn>

                        </DataGrid.Columns>
                    </DataGrid>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ListBox>

It looks ok.

But when I do horizontal scrolling by quckly dragging the thumb, strange extra space appears.

And when I resize the window, that extra space magically disappears. Where does it come from? How to get rid of it?

If I use simple StackPanel everything is fine, but I need to use virtualization.