There is a well-known issue with WPF RadioButton controls with data binding: when a radio button is unchecked the data binding is not undone. For example, suppose you have the following two radio buttons in the same group linked to a the "IsSuccess" (of type bool?) attribute of an object: <RadioButton Grid.Row="0" Grid.Column="0" GroupName="rbGroup" Margin="8,0,0,0" VerticalAlignment="Center" Content="Success" x:Name="rbSuccess" IsChecked="{Binding Path=IsSuccess, Mode=TwoWay, Converter={StaticResource ......