In the header of this theme appears the word “// archives” when you are browsing them. Galician (gl.) version shows a mistaken translation: “// ficheiros”. I could not find this string in GlotPress in order to fix it. The translation should be “// arquivo” or “// arquivos”.
Hello ludusnaturae, it seems that you managed to find the correct string on the same day, I see your translation for “Archives” here. Looks like you were not finding it because “// ” was part of the design, not the actual string.
That said, The Morning After theme is currently pulling the translations into the Appearance > Theme Options screen, but not the actual header (doh!), as reported here. We are looking into this, thanks for your patience!