Solution : https://service.sap.com/sap/support/notes/535586 (SAP Service marketplace login required)
Key words : 
customer-specific relationship types, symptom sap bp conversion, attached correction instructions, relationship types 0020, shared apartment, 'group' indicator, terms rftbup01, business partner, rftbup02 reason, program error
Related Notes : 
       
| 398888 | BP_TR1: Composite note and FAQs about bus partner conversion |