import into termbase with sublanguages

Hi, I'm trying to import data into a termbase with sublanguages (ES-ES>EN-US/EN-GB).

I uncheck the "Ignore sublanguages" checkbox, but the import fails with the error: "Does not conform to the target termbase definition. Reason: Source: <language type="ES" lang="ES-ES"></language>"

My termbase definition has 3 languages: English (United Kingdom), English (United States) and Spanish (Spain).

My import file has terms tagged either <language type="ES" lang="ES-ES" />, <language type="EN" lang="EN-US" /> or <language type="EN" lang="EN-GB" />. No entry has all three languages, they all have ES and either GB or US (is that the problem?).

If I leave the Ignore sublanguage box checked, the data imports but the sublanguages are not recognised (all EN are terms imported as EN-GB).

What am I doing wrong? Thank you!