Solution : https://service.sap.com/sap/support/notes/1719798 (SAP Service marketplace login required)
Summary : 
      Files transferred from the SAP application server to a PC using RFASLDPC are unreadable due to byte order inconsistencies across differing system architectures (big endian, little endian) in SAP ERP environments. This issue arises particularly when files generated on a background server are moved via a dialog server to a PC. SAP Note 552464 provides additional insights into byte orders. To correct this, a new selectable option is added to RFASLDPC, allowing users to adjust byte order during file imports, ensuring compatibility and readability on local PCs.
Key words : 
short              10      byte ordermedium            20      change byte orderlong              40      reverse byte order, software component   sap_appl                      sap application, readingheading       30      reverse byte orderdocumentation, goto -> text elements -> selection texts, short descriptionreverse byte order, byte order mark reason, existing byte order mark, org/wiki/byte-reihenfolge, message message short text, character set conversions executed
Related Notes : 
       
| 1776497 | |
| 1319517 | Unicode Collection Note | 
| 1310720 | Collection Note for Unicode Systems with different endianess | 
| 552464 | What is Big Endian / Little Endian? What Endian do I have? |