Solution : https://service.sap.com/sap/support/notes/456858 (SAP Service marketplace login required)
Key words : 
mm potentially generate additional inconsistencies, additional key words m7301, generate error message m7301, invoices inexplicable amounts occur, affected purchase order item, purchase order history shows, affected purchase order items, quantity delivered = quantity invoiced, post additional goods receipts, purchase order item
Related Notes : 
       
| 413531 | MR01: BPMNG with planned delivery costs incorrect | 
| 393189 | MIRO: Incorrect update of BPMNG -> DYNPRO_FIELD_CONVERSION |