Hello Stefan,

I noticed this problem was raised in several posts:

https://www.infragistics.com/community/forums/f/ultimate-ui-for-wpf/110150/index-was-outside-the-bounds-of-the-array/518015#518015

https://www.infragistics.com/community/forums/t/91190.aspx

We use Infragistics 17.2.20172.1000. Sometimes (we couldn't exactly point out what was different) when modifying bounded Data, Data is not shown in the Grid and firing a propertychanged gives an exception. Our grid has multiple Layouts and we do not use threads.  Here is the StackTrace:

Index was outside of the array

  at Infragistics.Collections.SparseArray.ValidateIndex(Int32 index)
   at Infragistics.Collections.SparseArray.GetItem(Int32 index, ICreateItemCallback createItemCallback)
   at Infragistics.Windows.DataPresenter.UnsortedRecordSparseArray.GetItem(Int32 index, Boolean create, Boolean calledFromSortedManagerSparseArray, Boolean& newRowCreated)
   at Infragistics.Windows.DataPresenter.UnsortedRecordSparseArray.GetItem(Int32 index, Boolean create)
   at Infragistics.Windows.DataPresenter.DataRecordCollection.get_Item(Int32 index)
   at Infragistics.Windows.DataPresenter.DataItemRecordMap.CheckMap(Object item, Func`1 getRecord)
   at Infragistics.Windows.DataPresenter.DataRecordCollection.LoadDataItemRecordMap(DataItemRecordMap dataItemRecordMap, Boolean recursive)
   at Infragistics.Windows.DataPresenter.DataPresenterBase.GetRecordsFromDataItems(Object[] dataItems, Boolean recursive)
   at Infragistics.Windows.DataPresenter.DataPresenterBase.ProcessPendingSelectedDataItems()
   at Infragistics.Windows.DataPresenter.DataPresenterBase.OnSelectedDataItemChanged(DependencyObject target, DependencyPropertyChangedEventArgs e)
   at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
   at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
   at Infragistics.Windows.DataPresenter.DataPresenterBase.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
   at Infragistics.Windows.DataPresenter.XamDataGrid.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
   at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
   at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
   at System.Windows.DependencyObject.InvalidateProperty(DependencyProperty dp, Boolean preserveCurrentValue)
   at System.Windows.Data.BindingExpressionBase.Invalidate(Boolean isASubPropertyChange)
   at System.Windows.Data.BindingExpression.TransferValue(Object newValue, Boolean isASubPropertyChange)
   at MS.Internal.Data.PropertyPathWorker.UpdateSourceValueState(Int32 k, ICollectionView collectionView, Object newValue, Boolean isASubPropertyChange)
   at MS.Internal.Data.ClrBindingWorker.OnSourcePropertyChanged(Object o, String propName)
   at System.Windows.WeakEventManager.ListenerList`1.DeliverEvent(Object sender, EventArgs e, Type managerType)
   at System.ComponentModel.PropertyChangedEventManager.OnPropertyChanged(Object sender, PropertyChangedEventArgs args)

   at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)