Hi,
Believe me, I have A LOT of experience setting WordPress translation as I am not English native speaker myself.
The issue seems to be related to how your plugin processes the array as I have never had similar issue before.
I will set a file for you to try with TwentyFifteen. (I think I’ve explained the issue well, anyway).
I will also give you better link for WP translations: http://www.cssigniter.com/ignite/wordpress-poedit-translation-secrets/
Regards,
Oliver
