ListViewHeader with StackLayout IsVisible does not work in OnAppearing

Hello!

I have a listView with a StackLayout and a ContentView in it´s HeaderTemplate.
This ContentView has a BindableProperty for IsVisible (default false).

    <ListView Header="{Binding .}">
                <ListView.HeaderTemplate>
                    <DataTemplate>
                            <StackLayout Spacing="0">
                                <ContentView BackgroundColor="Blue" IsVisible="{Binding BlueBlock}">
                                    <Label TextColor="White" Text="Blue Block" />
                                </ContentView>
                            </StackLayout>
                    </DataTemplate>
                </ListView.HeaderTemplate>
           </ListView>

When I call
BlueBlock= true;
in OnAppearing nothing happens.

But

• when I use true as default for IsVisible the Block will be displayed.
• when I call BlueBlock = true in a button click, the block also appears (after the second time).

I have created a SampleApp to reproduce this problem.

Why doesn´t it work in OnAppearing?
Is this a bug, or am I doing something wrong?

The problem appears in Android.
Xamarin.Forms: 2.3.4.224
VisualStudio 2017 Enterprise (15.1)
Xamarin: 4.4.0.34
Xamarin.Android.SDK: 7.2.0.7

Thanks in advance,
Stefan