RF_006: UTF-8 byte-order mark present (accepted by the ESAs, rejected by some portals)
Note
What triggers it
A file starts with the UTF-8 byte-order mark (Excel adds one when saving as CSV UTF-8).
How to fix it
Nothing to do for the ESAs, who accept it. Some national portals and older tools reject it; the Roifile packager removes it.
Source: EBA slide 30 of the common-issues deck.