Usually for subcontracting item(order category-70) PO is only allowed to be created through PO proposal(PPS170).
In my situation have PO(in PPS200) when I try to add new subcontracting item to PO lines it gives me message 'A purchase order for subcontracting cannot be entered in PS200.Use PPS170 instead.(PPS201/B1-10:03 AM-PP20017-20)'
Want to be sure if there is fix OR other way to add new PO lines to existing PO for subcontracting item(s).