Missing Symbols after resuming windows in Xamarin.forms app - xamarin.forms

Question

I have a Multiplattform app in Xamarin.forms for iOS, Android and UWP.
I'm using materialdesignicons-webfont.ttf for all my symbols.
If the windows goes in standby mode and resume after that, all symbols are missing.
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:SymbolTest"
x:Class="SymbolTest.MainPage">
<ContentPage.Resources>
<ResourceDictionary>
<OnPlatform x:Key="MaterialFontFamily" x:TypeArguments="x:String">
<On Platform="UWP" Value="Assets/Fonts/materialdesignicons-webfont.ttf#Material Design Icons" />
</OnPlatform>
</ResourceDictionary>
</ContentPage.Resources>
<StackLayout>
<Label Text="" HorizontalOptions="Center"
VerticalOptions="CenterAndExpand" >
<Label.FontFamily>
<OnPlatform x:TypeArguments="x:String">
<On Platform="UWP" Value="Assets/Fonts/materialdesignicons-webfont.ttf#Material Design Icons" />
</OnPlatform>
</Label.FontFamily>
</Label>
<Button Grid.Column="1" x:Name="btnSearch" BackgroundColor="LightBlue" >
<Button.ImageSource>
<FontImageSource FontFamily="{StaticResource MaterialFontFamily}" Size="36" Glyph="" Color="SlateGray" />
</Button.ImageSource>
</Button>
</StackLayout>
</ContentPage>
The ButtonImage ist missing the Label.Text is not missing

Answer 1

Missing Symbols after resuming windows in Xamarin.forms app
I created code sample follow this tutorial, And it works well if I sleep the computer and resuming, please check the following code if you have missed some key procedure.
<Label Text="">
<Label.FontFamily>
<OnPlatform x:TypeArguments="x:String">
<On Platform="UWP" Value="Assets/Fonts/materialdesignicons-webfont.ttf#Material Design Icons" />
</OnPlatform>
</Label.FontFamily>
</Label>
Update
I could reproduce your issue, and it only occurs in reference StaticResource scenario, it looks a bug, please feel free post the bug report in Xamarin github, and I will report it to related team.