I don't mean the system language (Windows' language), I mean the Minecraft language.
I get the same problem if I set Minecraft to Korean (KR). Galacticraft items were not translated to the most languages available in Minecraft, that is why your game displays blanks instead of actual texts.
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micdoodle8 : you could make GC use English strings when a selected language string is not found/translated. But I am not sure if Minecraft has some restriction against it.