Solution : https://service.sap.com/sap/support/notes/520826 (SAP Service marketplace login required)
Key words : 
dobject class     bupaopobject typefunction module  pi_bp_customer_main_extractnew entry, dobject class     bupaopobject typefunction module  pi_bp_customer_rel_extractyou, short text 'data extractor relationships, create function module pi_bp_customer_rel_extract, create function module pi_bp_customer_rel_send, pi 2002_1 support package 01, function group ccco, terms bp_exchange_r3_to_crm reason, source code corrections, attached correction instruction
Related Notes : 
       
| 702992 | The Initial/Request Download of object CUSTOMER_REL | 
| 541149 | Corrections for Note 520826 | 
| 537486 | Composite SAP note:perfrmnce problms during initial download | 
| 523003 | Initial download CUSTOMER_REL: long runtimes in R/3 |