Solution : https://service.sap.com/sap/support/notes/523003 (SAP Service marketplace login required)
Key words : 
long runtimes occur, terms bp_exchange_r3_to_crm reason, source code corrections, contact person data, data extraction, initial download, object customer_rel, partner functions, program error, solution implement
Related Notes : 
       
| 537486 | Composite SAP note:perfrmnce problms during initial download | 
| 520826 | Initl download CUSTOMER_REL:Too many relationships per block |