CollectionView child added event not firing - xamarin

Question

I am using Xamarin Forms and CollectionsView.I am adding Frame child rows using SignalR. Child added event is not firing after few child is added.Is it a bug or am i doing something wrong?? I tried with CollectionView_ChildAdded event also.That one also gives this unexpected behavior
<CollectionView x:Name="ItemsListView"
ItemsSource="{Binding Items}"
VerticalOptions="FillAndExpand"
SelectionMode="None"
ItemsUpdatingScrollMode="KeepScrollOffset"
>
<CollectionView.ItemTemplate>
<DataTemplate>
<Frame x:Name="frame1" BackgroundColor="White" BorderColor="#F0F0F0" Padding="3" Margin="0,0,0,5" HasShadow="False" CornerRadius="10" ChildAdded="frame1_ChildAdded">
<Grid HeightRequest="40" HorizontalOptions="FillAndExpand" VerticalOptions="Start">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="2*"/>
<ColumnDefinition Width="2*" />
<ColumnDefinition Width="6*" />
</Grid.ColumnDefinitions>
<Label Grid.Column="0" x:Name="lb_TicketNumber" Text="{Binding TicketNumber}" TextColor="Black" FontSize="Large" FontAttributes="Bold" VerticalOptions="Center" Margin="20,0" HorizontalTextAlignment="Center" />
<Label Grid.Column="1" Text="{Binding DeskName}" TextColor="Black" FontSize="Large" FontAttributes="Bold" VerticalOptions="Center" HorizontalTextAlignment="Center"/>
<Label Grid.Column="2" Text="{Binding ServiceNameEng}" TextColor="Black" FontSize="Large" FontAttributes="Bold" VerticalOptions="Center" HorizontalTextAlignment="Center" />
</Grid>
</Frame>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
below event stops firing after few times.
private void frame1_ChildAdded(object sender, ElementEventArgs e)
{
DisplayAlert("Item added", "OK", "OK");
}