Solution : https://service.sap.com/sap/support/notes/720720 (SAP Service marketplace login required)
Key words : 
user exit de_bcs2s reason, user exit de_bcs2s, user exits pi_bp_de_bcs2s_kna1, function modules pi_bp_de_bcs2s_kna1, function module accroding, customer master data, header specific information, correction instruction provided, header information, updated data
Related Notes : 
       
| 617221 | PIDE not taken into account in user exit DE_BCS2S |