Solution : https://service.sap.com/sap/support/notes/132143 (SAP Service marketplace login required)
Summary : 
      After implementing Note 112062, users encountering error messages MM104 or MM103 when creating a production order or costing that involves a phantom in the bill of materials may be due to an item lacking a material number. This primarily affects non-stock, text, or document items within the phantom bill of materials. The underlying issue stems from a source code error. To resolve these errors, the source code must be corrected appropriately to handle such scenarios.
Key words : 
system generates error message mm104 'material, additional key words co01, material number, mm103 'material &, implement note 112062, production order, document item, source code, solution correct, prerequisites
Related Notes : 
       
| 331809 | No conversion base unit of measure of component | 
| 147672 | Header quanty change: Scrap not taken into account | 
| 126201 | CO01:Error ME101 after implmentation of Note 112062 | 
| 122583 | Trmntn 'NOT_FOUND' after implmntatin of Note 112062 | 
| 112062 | CO01/02:Incor. phantm qties when changing headr qty |