It's due to Joomlas language filter plugin settings the Joomla application language very late. CB loaded its API before Joomlas has processed the language code in the URL. This causes CBs API to load with the previous application language, which is why it looks like it's 1 page load behind. I've added a bug ticket to CB as we'll have to probably reload the language in our system plugin to avoid this caching problem. For now the only workaround I can suggest is to disable the CBSubs system plugin, but that's only acceptable depending on what you're protecting.
forge.joomlapolis.com/issues/5360