When creating another language version the internal links to other pages are not updated, so they still point to pages in the default language. For example, we used English as our default language, but when we created the Spanish version and translated our content, all links on the Spanish site link to English pages.
This issue was recently fixed when creating a new version based on an existing version, so that links would be automatically updated to point to the correct version - we need something similar so we don't need to manually update every link on the site for each new language.