https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/WikibaseMediaInfo/+/23e6e07652a171237f975e2763f5c7a626ac7333/i18n/en.json in wikibasemediainfo-time-precision-year1k, "millenium" should be "millennium".
https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/WikibaseMediaInfo/+/23e6e07652a171237f975e2763f5c7a626ac7333/i18n/en-gb.json - wikibasemediainfo-special-mediasearch-continue is not in English, and doesn't need a separate translation for British English. It was created at TranslateWiki, "Translation updater" copied it, it was deleted at TranslateWiki, then FuzzyBot copied the bad translation back to TranslateWiki.
It looks like because they have the MediaWiki: prefix, they are protected from translation, also it doesn't allow editing the English versions of messages.