Gridview displayes only 2 Item per Group

Question

My Gridview works well, but there is a problem i cant figure out since a while. The Gridview displayes not more the 2 Items per group. The ItemTemplate and the incoming List are valid.

<GridView   x:Name="mainGridView" ItemsSource="{Binding Source={StaticResource groupedItemsViewSource}}" 
                                                SelectionMode="Multiple" IsItemClickEnabled="True" ItemClick="GridView_ItemClick_1" Grid.Row="1" 
                                                Margin="0,-3,0,0" Padding="116,25,40,46" 
                                                FontFamily="Global User Interface"  ItemTemplate="{StaticResource mainPageTileTemplates}"
                                                ItemContainerStyle="{StaticResource GridViewItemStyleStretch}" SelectionChanged="Item_selected" >



                    <GridView.GroupStyle>
                        <GroupStyle>
                            <GroupStyle.HeaderTemplate>
                                <DataTemplate>
                                    <TextBlock Text='{Binding Key}'  Foreground="#FF116C15" Margin="5" FontSize="28" FontFamily="Segoe UI Light" />
                                </DataTemplate>
                            </GroupStyle.HeaderTemplate>
                            <GroupStyle.ContainerStyle>
                                <Style TargetType="GroupItem">
                                    <Setter Property="Template">
                                        <Setter.Value>
                                            <ControlTemplate TargetType="GroupItem">
                                                <StackPanel Orientation="Vertical">
                                                    <ContentPresenter Content="{TemplateBinding Content}" />
                                                    <ItemsControl x:Name="ItemsControl" ItemsSource="{Binding GroupItems}" />
                                                </StackPanel>
                                            </ControlTemplate>
                                        </Setter.Value>
                                    </Setter>
                                </Style>
                            </GroupStyle.ContainerStyle>
                            <GroupStyle.Panel>
                                <ItemsPanelTemplate>
                                    <VariableSizedWrapGrid Orientation="Vertical"  MaximumRowsOrColumns="5" />
                                </ItemsPanelTemplate>
                            </GroupStyle.Panel>
                        </GroupStyle>
                    </GridView.GroupStyle>
                    <GridView.ItemsPanel>
                        <ItemsPanelTemplate>
                            <WrapGrid Orientation="Vertical" MaximumRowsOrColumns="1" />
                        </ItemsPanelTemplate>
                        </GridView.ItemsPanel>
                    <Button Visibility="Collapsed"/>
                </GridView>

Answer 1

Maybe in your GroupItems collection you're binding the elements only to a Top collection that only contains the first 2 elements (as the template does, but with 12 elements on the Top). Check de Path of GroupItems.