Solution : https://service.sap.com/sap/support/notes/490906 (SAP Service marketplace login required)
Key words : 
double-clicking form stufe_weg_renumber, symptom note 431085 makes, directly manufactured assemblies, form-routine, implement note 431085, collective orders, individual order, phantom assemblies, phantom assembly, terms aufwg
Related Notes : 
       
| 431085 | More than 99 assemblies on one level in collective order |