Grouped listview / Header rows have improper height on iOS only

Hi,

This listview is OK and Android, but NOT OK on iOS.
The header rows (even height) have improper height. Interestingly, uneven sub-item rows have proper height.

What could be the reason, and how to "fix" it?

See image, left is real GUI (from iOS Simulator), right side is how it should look like (and looks on Android)

     <ListView  HasUnevenRows="True" IsGroupingEnabled="True" >
            <ListView.GroupHeaderTemplate>
                <DataTemplate>
                    <ViewCell>
                        <ContentView Padding="5">
                                <Grid>
                                    <Grid.RowDefinitions>
                                        <RowDefinition Height="Auto" />
                                        <RowDefinition Height="Auto" />
                                    </Grid.RowDefinitions>
                                    <Grid.ColumnDefinitions>
                                        <ColumnDefinition Width="*" />
                                        <ColumnDefinition Width="Auto" />
                                    </Grid.ColumnDefinitions>

                                    <.... LABELS  in grid cells....>

                                </Grid>
                        </ContentView>
                    </ViewCell>
                </DataTemplate>
            </ListView.GroupHeaderTemplate>

            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <ContentView Padding="20,5,10,5">
                            <Grid>
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="Auto" />
                                </Grid.RowDefinitions>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="Auto" />
                                    <ColumnDefinition Width="*" />
                                    <ColumnDefinition Width="Auto" />
                                </Grid.ColumnDefinitions>

                                <.... IMAGE and LABELS in grid cells.....>

                            </Grid>
                        </ContentView>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

Thanks