Solution : https://service.sap.com/sap/support/notes/73259 (SAP Service marketplace login required)
Key words : 
additional key words transactions co40, phantom material occurs repeatedly, multi-level bills, inserting phantom items, phantom material, phantom item, phantom bom, production order, transaction co01, random operation
Related Notes : 
       
| 164510 | CO40: Part to be discontinued deleted w/o successor | 
| 121212 | Component assignment of direct production assmblies | 
| 93776 | CO01: Component allocation after upgrade from 2.2* | 
| 93586 | Process order: sequence of the materials | 
| 91179 | Validity of component allocation in prodn. order | 
| 85441 | Component allocation when looking up master data | 
| 82838 | Component allocation of assemblies (prodctn order) | 
| 82644 | Component allocation of phantom assemblies (routing) | 
| 81656 | CO01: Component allocation in the collective order | 
| 78747 | COR2/CO02 with alternative components: Short dump | 
| 75943 | Incorrect component allocatn for phantom assemblies | 
| 73107 | Allocation of phantom assemblies in productn order | 
| 67515 | CO01:Wrong component allocation f.phantom assembly | 
| 50454 | CO40: Incorrect component assignmnt/backflush indic. | 
| 46790 | Incorrect component allocatn in production order | 
| 42198 | Clear duplicate material component assignments |