Japanese version of AMP Fest 2020 event page contains untranslated English text

Description

While browsing the Japanese version of the AMP Fest 2020 event page, I noticed that a large portion of the content is still displayed in English even though the language is set to JA. The language switcher updates the URL and navigation correctly, but the main headings and page text don’t change.

Reproduction Steps

URL:- https://amp.dev/ja/events/amp-fest-2020

Steps to Reproduce
Open the page above
Ensure language is set to JA (Japanese)
Observe page content
Expected Behavior
All visible text should appear in Japanese when JA locale is selected.

Actual Behavior
Large portions of text (e.g., "Rewatch the talks", event descriptions, section headings)
remain in English even on the Japanese version.

Tested Environments
Browser: Brave (stable)
Also tested in Incognito mode — same result
OS: Linux
Relevant Logs
Browser(s) Affected
No response

OS(s) Affected
No response

Device(s) Affected
No response

AMP Version Affected
No response

Open https://amp.dev/ja/events/amp-fest-2020 and locate the source content and Japanese translation entries for the AMP Fest 2020 page. Compare the visible headings, event descriptions, and “Rewatch the talks” text with the JA locale, then verify that all visible page text is Japanese when the locale is selected.

Written by the indexing model from the issue text.