Solution : https://service.sap.com/sap/support/notes/139908 (SAP Service marketplace login required)
Key words : 
correct quantity distribution, note replaces note 101007, entered components, parallel discontinuation, production order, availability check, stock situation, distributed correctly, header quantity, system displays
Related Notes : 
       
| 328844 | Variable-size items as parts to be discontinued | 
| 101007 | Wrong qantty t.be dscntnud for header qantty change |