Hello everyone,
I've found a workaround for my problem. Riku, you were right, it was indeed a memory issue. The CPK file must have been getting to big. Turns out the biggest file in the archive is a font file, containing all the fonts of the game (except fur cutscenes subtitles). So there is indeed a lot a kanas and kanjis. But all thoses won't be needed in the translation, leaving us with a way smaller file. And that's enough to do the trick.
The workaround holds until the translations grows too big, but that's already something, at least.
I've found a workaround for my problem. Riku, you were right, it was indeed a memory issue. The CPK file must have been getting to big. Turns out the biggest file in the archive is a font file, containing all the fonts of the game (except fur cutscenes subtitles). So there is indeed a lot a kanas and kanjis. But all thoses won't be needed in the translation, leaving us with a way smaller file. And that's enough to do the trick.
The workaround holds until the translations grows too big, but that's already something, at least.