[Winphone8] Performance of xamarin form in Winphone8

I have a project that 1 homepage contains serveral items (contaner is not a listview). Each item is a view and I added manually. And something may be goes wrong, the application runs quite slow. It take over 3 seconds to load one item (device : Nokia 520). With 20 items, it took over 2 minutes . I have checked on output window, seem to be every time a item loading, two exception named ArgumentException and AmbiguousMatchException have been thrown.

Could every body can check what I did wrong with HomePageItem.xaml to cause it runs slow ? I'v attached the file below.
Thank in advanced.