Windows Phone 8.1 (RT) ListView ObservableCollection Add results in HRESULT E_FAIL

Hello,

I'm currently experiencing a Problem when adding items to my ListView through an observable collection (currently using 1.5.0-pre3).
(Android/iOS working fine)

Has anyone experienced the same?

 Error HRESULT E_FAIL has been returned from a call to a COM component.

   at Xamarin.Forms.TemplatedItemsList`2.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   at Xamarin.Forms.TemplatedItemsList`2.OnProxyCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e, Boolean fixWindows)
   at Xamarin.Forms.TemplatedItemsList`2.OnProxyCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   at Xamarin.Forms.ListProxy.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   at Xamarin.Forms.ListProxy.<>c__DisplayClass52_0.<OnCollectionChanged>b__0()
   at Xamarin.Forms.ListProxy.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   at Xamarin.Forms.ListProxy.WeakNotifyProxy.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   at FormsApp.ObservableCollection`1.Add(ContactModel contact) 
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)