Solution : https://service.sap.com/sap/support/notes/361668 (SAP Service marketplace login required)
Key words : 
configurable sales order item, sales order item, program error solution, individual customer requirement, characteristic 'material variant', characteristic configurable, production order, collective requirement, material variant, characteristic valuation
Related Notes : 
       
| 631062 | Configuration with individual requirements | 
| 551200 | Update termination after inserting phantom assembly | 
| 519044 | Enhancement subnetwrk possible in sp of product cost collctr | 
| 359467 | BOM - explosion material variant |