And speaking from personal experience, Yahoo! JAPAN does not archive all news articles forever.
Some news links are deleted after a certain period, and you may see a "Page Not Found" message if you are searching old links from other forums, blogs, etc...
Perhaps this is due to the strict copyright management of Japanese companies.
(You may want to use sites like archive.today for archiving long time.)
I think this might be the reason why the content is not translated properly, maybe to prevent automatic scraping.
Edit - Even the support page requires JavaScript to be enabled.
https://support.yahoo-net.jp/PccNews/s