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If I understand correctly the scenario you have implemented a custom drag drop functionality with the DragDropManager and have used the ListBoxDragDropBehavior
at same time in order to enable reordering? We don't recommend using both approaches together as this may cause such issues. However what I can suggest you is to check the attached sample project which demonstrates how to implement reordering of the ListBoxItems using only the DragDropManager.
Hope this helps.
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