When a SortDesciptor is applied and items are modified, the selection behaves inconsistently:

1. If an item is modified, so it's position needs to be changed according to the sorting descriptor, it will be removed from the SelectedItems.
2. If an item is modified, but it's position should remain the same, it remains in the SelectedItems collection.
2a. If IsSynchronizedWithCurrentItem item is set to true and the position should remain the same, the item is removed from the SelectedItems and the one that goes in the same position is added to the collection.

Workaround is to add the item back to the SelectedItems collection when RowEdit ends.

private void clubsGrid_RowEditEnded(object sender, GridViewRowEditEndedEventArgs e)
{
    (e.Source as RadGridView).SelectedItems.Add(e.NewData as Club);
}