Solution : https://service.sap.com/sap/support/notes/629934 (SAP Service marketplace login required)
Key words : 
execute backorder processing, early confirmation reason, source code corrections, changed items, distribution documents, oltp system, delivery date, updated incorrectly, terms update, program error
Related Notes : 
       
| 382746 | Collective note: Delivery+transportation scheduling with APO | 
| 375193 | Backorder processing: Composite SAP note on posting |