When entering a Sales Order, if an item is selected as "drop ship" from the vendor, and the information for the vendoe is provided, a PO is automatically produced.  When the item is direct drop shipped, it is processed by clicking the "mark shipped" button which fulfills the item and takes you directly through receipt of the item and thru item fulfillment.  If however, prior to the item being shipped, the PO is edited and an additional item added, regardless if it is added as Drop Ship or otherwise, when the "mark shipped" button is clicked, the only option available