Change in WBS element in a PO

Hi

In my Purchase Order, earlier it was account assigned to a WBS element A. When we ran CJI3, it showed the same. But now the account assignment of WBS element was changed to B. I have no idea how this got changed. I only can check from the Purchase Order history and founf that "Profit center has been changed for the item".

How this could have happened? Any info reg this will be helpful. Thanks.