Solution : https://service.sap.com/sap/support/notes/450520 (SAP Service marketplace login required)
Key words : 
error message f5a251, message class f5a, create message 251, outgoing payment, check printout, payment document, payr-vblnr, update terminations, syslog sm21, terms fbz4
Related Notes : 
       
| 175047 | Causes for FI document number gaps (RF_BELEG) |