Hey @B,
It sounds like your translation files are simply out of date, which is unfortunately some bad news and there is not much that can be done other than manually updating your .mo and .po files.
This happens because, with every plugin update, the code of the plugin changes. Thus, every update there are some new strings added, some strings are deleted, and others are changed, so the main plugin .pot file is updated with each release.
If your .mo and .po files are not up to date with that .pot file, there will be translations issues like the ones you describe here.
If you want to run versions 3.12 of our plugins, you will unfortunately need to update your translation files or hold out until another member of the community updates them. If you’re curious about how to access/contribute to translation files, we have articles on these topics as follows:
• Translating The Events Calendar: http://theeventscalendar.com/knowledgebase/translating-the-events-calendar/
• Translating our premium add-ons: https://theeventscalendar.com/knowledgebase/adding-or-updating-a-translation/
• Changing the language on your site: https://theeventscalendar.com/knowledgebase/changing-the-language-on-your-calendar/
I hope this all helps!
— George