System.ArgumentOutOfRangeException when scrolling in a Listview with Custom GroupHeaderTemplate

Hi, as said in the title, I have a listview filled with Contacts that i ordered in groups with grouping, I binded GroupDisplayBinding with the Key of each group.
Like that I have a list of contacts with a header showing key corresponding to the group of contacts like here :
motzcod.es/post/94643411707/enhancing-xamarin-forms-listview-with-grouping-headers

I made a custom header for this GroupHeaderTemplate:

       public class HeaderCell : ViewCell
        {
            public HeaderCell()
            {
                var title = new Label()
                {
                    Font = Font.BoldSystemFontOfSize(NamedSize.Small),
                    TextColor = Color.Black,
                    VerticalOptions = LayoutOptions.Center
                };

                title.SetBinding(Label.TextProperty, "Key");

                View = new StackLayout
                {
                    HorizontalOptions = LayoutOptions.Fill,
                    HeightRequest = 25,
                    BackgroundColor = Color.FromRgb(52, 152, 218),
                    Padding = 5,
                    Orientation = StackOrientation.Horizontal,
                };
            }
        }

and linked it to my listview:

    var contacts = new ListView();
            content.Children.Add(contacts);
            contacts.SetBinding(ListView.ItemsSourceProperty, new Binding("ContactsGrouped"));
            contacts.IsGroupingEnabled = true;
            contacts.GroupDisplayBinding = new Binding("Key");
            contacts.GroupShortNameBinding = new Binding("Key");
            contacts.SetValue(Grid.RowProperty, 1);
            contacts.SetValue(Grid.ColumnProperty, 0);
            contacts.HorizontalOptions = LayoutOptions.FillAndExpand;
            contacts.RowHeight = 80;           
            contacts.ItemTemplate = new DataTemplate(typeof(ContactCell));   
            if (Device.OS != TargetPlatform.WinPhone)
                contacts.GroupHeaderTemplate = new DataTemplate(typeof(HeaderCell));
            contacts.HasUnevenRows = true;

My problem is that if I use a DataTemplate for my GroupHeaderTemplate, I got ArgumentOutOfRangeException when I scroll down my list even if all code in my DataTemplate is commented, but if let the default template, it works.

I don't know if that's a problem with Xamarin or if there's really something with my code so if someone already had this problem or knows something about this issue please tell me.
I found out that some people had the same problem in this thread but no real solution was given :
forums.xamarin.com/discussion/19714/listview-for-android-crashing-on-scroll-when-populated-with-custom-fontawesome-label