I think something with the theme translation doesn’t work when your site’s default locale is not English (US). When I set it to English (US), the Search Banner works with its default settings for every user’s locale
(English (US), English (UK), & German)
But when I change the site’s default locale to English (UK), without editing the Theme’s settings, the banner is broken in English US:
(English (US), English (UK) & German)
The same happens when I choose German as the site’s default locale.