My request for the other raw file overlapped your post where you noted that raw conversion always showed the problem - even using X Raw Studio.
The bottom line is that its best to avoid lossy compressed raw to be safe.
I tried the sample you posted in X Raw Studio and it gives the same problem as the other raw converter.
Can you post a link to the other raw - where X Raw Studio appears to avoid the artefacts?
Its probably a good idea to avoid shooting in compressed raw as it doesn't buy you all that much space over lossless compressed.
EDIT: I see you have now posted that you have the same problem with X Raw Studio - which is what I expected - the problem seems to be with the lossy compression algorithm that FujiFilm uses.
