Solution : https://service.sap.com/sap/support/notes/331809 (SAP Service marketplace login required)
Key words : 
additional key words co02, total quantity, system calculates, requirement quantities, incorrect factor, phantom assembly, maintained differently, inserted manually, requirement quantity, program error
Related Notes : 
       
| 377648 | Incorrect requiremt quantity after header change in quantity | 
| 187110 | Incorrct qties for components of a phantom assembly | 
| 132143 | MM104 or MM103 after implementation of Note 112062 | 
| 112062 | CO01/02:Incor. phantm qties when changing headr qty |