Solution : https://service.sap.com/sap/support/notes/941300 (SAP Service marketplace login required)
Key words : 
includes goods receipt documents, prerequisites program error solution, delivery complete indicator, program correction, deletion indicator, purchasing document, ekpo-elikz, ekpo-loekz, order quantity, po history
Related Notes : 
       
| 1142061 | S013-PWMT S012-MABW incorrect or negative value for quantity | 
| 1044799 | Negative score for S013-PWMT & S012-MABW | 
| 979236 | Negative or incorrect score for S013-PWMT & S012-MABW | 
| 877786 | Valuated blocked stocks - movements 107 and 109 | 
| 865034 | |
| 647025 |