WPF DataGrid right click selection row with DataGridcolumnTemplate

Question

In a WPF DataGrid right-clicking on a row selects the row. In this example of DataGrid with 2 Columns, when I right-click on a row of the DataGridTemplateColumn, nothing happens. If I right-click on a row the DataGridTextColumn the row is selected and the Background Color is set to blue. The strange thing is that if I right-click on the DataGridTemplateColumn once, then the selection row works correctly. To reproduce it, first right-click on a row on the DataGridTemplateColumn, then right-click on another row and finally right-click again on the first clicked row on the DataGridTemplateColumn, and then the selection works.

How to get the row selection when right-clicking once on a row on the DataGridTemplateColumn ?

XAML

<DataGrid ItemsSource="{Binding SourceList}"
          SelectedItem="{Binding SelectedSource}"
          Height="auto"
          IsReadOnly="False"
          AutoGenerateColumns="False">
    <DataGrid.Columns>
        <DataGridTextColumn Header="NameText" Binding="{Binding NameText}" Width="*"/>
        <DataGridTemplateColumn Header="Template" Width="*">
             <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <ComboBox ItemsSource="{Binding ComboCheck}">
                        <ComboBox.ItemTemplate>
                            <DataTemplate>
                                <StackPanel Orientation="Horizontal">
                                    <CheckBox IsChecked="{Binding IsChecked, UpdateSourceTrigger=PropertyChanged}" />
                                    <TextBlock Text="{Binding Program}" Width="100" />
                                 </StackPanel>
                            </DataTemplate>
                        </ComboBox.ItemTemplate>
                    </ComboBox>
                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>
    </DataGrid.Columns>
</DataGrid>

THE VM

public class MainVM
{
    private ObservableCollection<SelectableModelData> myNamesList = new ObservableCollection<SelectableModelData>()
    {
        new SelectableModelData(new ModelData<string>("name 1 obj", "name 1 text"), true),
        new SelectableModelData(new ModelData<string>("name 2 obj", "name 2 text"), true),
        new SelectableModelData(new ModelData<string>("name 3 obj", "name 3 text"), true)
    };
    private List<SourceTest> mySourceList;

    public MainVM()
    {
        mySourceList = new List<SourceTest>();

        SourceTest t = new SourceTest("Text 1", myNamesList[0], true, 0);
        t.ComboCheck.Add(new Programs("yes", true));
        t.ComboCheck.Add(new Programs("no", false));
        mySourceList.Add(t);

        t = new SourceTest("Text 2", myNamesList[1], true, 1);
        t.ComboCheck.Add(new Programs("yes", true));
        t.ComboCheck.Add(new Programs("no", false));
        mySourceList.Add(t);

        t = new SourceTest("Text 3", myNamesList[2], true, 2);
        t.ComboCheck.Add(new Programs("yes", true));
        t.ComboCheck.Add(new Programs("no", false));
        mySourceList.Add(t);
    }

    public List<SourceTest> SourceList => mySourceList;
    public SourceTest SelectedSource { get; set; }
}

ASSOCIATED CLASSES

public class Programs
{
    public Programs(string prog, bool check)
    {
        Program = prog;
        IsChecked = check;
    }

    public bool IsChecked { get; set; }
    public string Program { get; set; }
}

public class SourceTest
{ 
    public SourceTest(string text, SelectableModelData sourceSMD, bool male, int index)
    { 
        SourceSMD = sourceSMD;
        NameText = text;
        Male = male;
        Female = !male;
        Index = index;

        ComboCheck = new ObservableCollection<Programs>();
    }

    public SelectableModelData SourceSMD { get; set; }
    public string NameText { get; set; }
    public bool Male { get; set; }
    public bool Female { get; set; }
    public int Index { get; set; }
    public bool IsAllowed { get; set; }
    public ObservableCollection<Programs> ComboCheck { get; set; }
}

public class SelectableModelData : ObservableObject
{
    private bool myIsSelectable;

    public SelectableModelData(ModelData<string> name, bool isselectable)
    {
        SModelData = name;
        IsSelectable = isselectable;
    }
    public bool IsSelectable
    {
        get { return myIsSelectable; } 
        set
        {
            if(myIsSelectable = value) return;
            myIsSelectable = value;
            OnPropertyChanged(nameof(IsSelectable));
        }
    }
    public ModelData<string> SModelData { get; set; }
}

public class ModelData<T>
{
    public ModelData() { }
    public ModelData(T item, string name)
    {
        Item = item;
        Name = name;
    }

    public T Item { get; private set; }
    public string Name { get; set; }
}