Assume that you have two sites, one is local and one is overseas. When the local one runs low, it creates a planned transfer order to the overseas one. If the overseas one runs low, it creates a planned purchase order. If there is nothing in stock at either site, the planned purchase order is done after the planned transfer order. This is not possible.
The changes in the hotfix use ReqDateDlvOrig to calculate transfer demand reqDate to make sure the planned transfer order and purchase order dates are correct when planning between two sites.