Solution : https://service.sap.com/sap/support/notes/73107 (SAP Service marketplace login required)
Key words : 
system allocate phantom assemblies, additional key words co01, prerequisites solution apply, general solution, wrong operation, production order, component allocation, order level, order path, program corrections
Related Notes : 
       
| 86748 | Material component allocation w. phantom assembly | 
| 73259 | CO01: Allocating components to an operation |