Let's use https://www.themoviedb.org/tv/65249 as example.

• Query: https://api.themoviedb.org/3/tv/65249/season/1/episode/1?api_key=key&language=en
  • Episode Name: "Flashing Before My Eyes"
  • OK
• Query: https://api.themoviedb.org/3/tv/65249/season/1/episode/1?api_key=key&language=en-US
  • Episode Name: "Flashing Before My Eyes"
  • OK
• Query: https://api.themoviedb.org/3/tv/65249/season/1/episode/1?api_key=key&language=zh-CN
  • Episode Name: "走马灯"
  • OK
• Query: https://api.themoviedb.org/3/tv/65249/season/1/episode/1?api_key=key&language=zh-HK
  • Episode Name: "走马灯"
  • OK
• Query: https://api.themoviedb.org/3/tv/65249/season/1/episode/1?api_key=key&language=zh-TW
  • Episode Name: ""
  • OK, since there is no record for zh-TW
• Query: https://api.themoviedb.org/3/tv/65249/season/1/episode/1?api_key=key&language=zh
  • Episode Name: "Episode 1"
  • WHY?

I cannot think of where could the API get the "Episode 1" value. I also don't know how to correct it, since we only support four-letter language+country code. Shouldn't we just fallback two-letter language code to the closest match?

This particular issue affects Plex TMDb agent since Plex only has setting for language, but not country. So their queries to TMDb use two-letter language code. As the result, I found the data I added in Mandarin (zh-CN) does not reflects in my Plex db .