When using a ListCollectionView with live sorting enabled, occasionally the CollectionChanged event will emit a NotifyCollectionChangedAction.Move notification where the NotifyCollectionChangedEventArgs.NewStartingIndex property doesn't match the actual index of the item in the collection found with ListCollectionView.IndexOf(object item).

If the collection view is used as an items source for a WPF component such as ListBox, this can result in incorrect sorting behavior or duplicate items appearing.

This seems to only occur for large collections (hundreds of items) where most of them have been marked for re-sort, presumably enough to meet ListCollectionView.LiveSortingDensityThreshold and trigger the LiveShapingList.RestoreLiveSortingByInsertionSort(...) code path.

I've attached a failing unit test demonstrating the problem. The expected behavior is that observing CollectionChanged events would be enough to keep an external collection in sync with the ListCollectionView items.

ListCollectionViewTests.cs.txt