Checked event firing when grouping added to DataGrid - WPF C#

I'm having a problem where when adding grouping to my datagrid; the event I have defined as "Checkbox.Checked" gets called when it shouldn't be. When this line of code is not commented out "collection.GroupDescriptions.Add(new PropertyGroupDescription("_group"));" the bug occurs.

Upon starting my application with this line in, the first check of any checkbox works as it should, then on the second click, if I click literally anywhere on the datagrid, the checked event will be fired.

Do any of you Stack Overflow geniuses have any idea?

Thanks.

I have events define on my DataGrid like this;

        <DataGridCheckBoxColumn.CellStyle>
                <Style>
                    <EventSetter Event="CheckBox.Checked" Handler="Method_checked"/>
                    <EventSetter Event="CheckBox.Unchecked" Handler="Method_Unchecked"/>
                </Style>
            </DataGridCheckBoxColumn.CellStyle>

I have since added grouping to my data using the following code in C#;

ListCollectionView collection = new ListCollectionView(listOfData);
            collection.GroupDescriptions.Add(new PropertyGroupDescription("_group"));
            dgData.ItemsSource = collection;

I have added groups to my datagrid adding the following code in xaml;

    <DataGrid.GroupStyle>
    <GroupStyle ContainerStyle="{StaticResource GroupHeaderStyle}">
            <GroupStyle.Panel>
                <ItemsPanelTemplate>
                    <DataGridRowsPresenter/>
                </ItemsPanelTemplate>
            </GroupStyle.Panel>
        </GroupStyle>
    </DataGrid.GroupStyle>

You may noticed "GroupHeaderStyle" which is defined above;

<Window.Resources>
        <Style x:Key="GroupHeaderStyle" TargetType="{x:Type GroupItem}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type GroupItem}">
                        <Expander x:Name="exp" IsExpanded="True"
                                  Background="White"
                                  Foreground="Black">
                                  <Expander.Header>
                                <TextBlock Text="{Binding Name}" />
                            </Expander.Header>
                            <ItemsPresenter/>
                        </Expander>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>