I'm seeing an issue with the following code:

<ig:XamComboEditor Grid.Row="0"
Grid.Column="0"
Margin="5,0,5,0"
ItemsSource="{Binding Path=AvailableGraphs}"
SelectedIndex="{Binding SelectedIndex}"
IsEditable="False">
<ig:XamComboEditor.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Left">
<Image Source="{StaticResource PieChartIcon}"
Width="16"
Stretch="Uniform"
Visibility="{Binding Type, Converter={StaticResource ChartTypeVisibilityConverter}, ConverterParameter=Pie}" />
<Image Source="{StaticResource BarChartIcon}"
Width="16"
Stretch="Uniform"
Visibility="{Binding Type, Converter={StaticResource ChartTypeVisibilityConverter}, ConverterParameter=Bar}" />
<Image Source="{StaticResource ColumnChartIcon}"
Width="16"
Stretch="Uniform"
Visibility="{Binding Type, Converter={StaticResource ChartTypeVisibilityConverter}, ConverterParameter=Column}" />
<Image Source="{StaticResource LineChartIcon}"
Width="16"
Stretch="Uniform"
Visibility="{Binding Type, Converter={StaticResource ChartTypeVisibilityConverter}, ConverterParameter=Line}" />
<TextBlock Text="{Binding Label}"
Margin="5,0,5,0"
FontWeight="Bold"
VerticalAlignment="Center" />
<TextBlock Text="{Binding Segment, Converter={StaticResource SegmentParenthesesConverter}}"
Margin="0,0,5,0"
VerticalAlignment="Center" />
</StackPanel>
</DataTemplate>
</ig:XamComboEditor.ItemTemplate>
</ig:XamComboEditor>

When I run this code and click on the combo editor, it alternates in the display behavior of the drop down menu's scroll bars.  Attached is an image showing the two states.

I am using v16.1.20161.2056.  Any suggestions are welcome.