Thetvdb addon uses wrong language

I've set RU as default lang in the thetvdb addon settngs.
But sometimes it displays EN names for tv series. And series list looks like that:

1. s01e01 <RU name>
2. s01e02 <RU name>
3. s01e03 <EN name>
4. s01e04 <RU name>
   

Why it uses wrong lang for names?