Solution : https://service.sap.com/sap/support/notes/595717 (SAP Service marketplace login required)
Key words : 
sym text                                  dl  ml 027 terms, 'basic data' tab page, 'payment' tab page, call transaction se38, enter program 'saplfdcb', select 'text elements', amount split reason, terms zterm, text elements, incorrect text
Related Notes : 
       
| 613761 | MIR4:Payment conditions are not displayed | 
| 546625 | EnjoySAP message F5A060 in tab page 'Amount split' |