Solution : https://service.sap.com/sap/support/notes/408028 (SAP Service marketplace login required)
Key words : 
additional key words matkl, generated work order, planned order conversion, resbd-matkl, planned order, production order, process order, material group, program error, solution implement
Related Notes : 
       
| 516986 | Purchase requisition generated for components | 
| 443191 | Material group (RESB-MATKL) when adding components |