You can check this post. This issue arises when the original language of the movie matches the language of the database on TMDB. In such cases, the translated title on TMDB is considered as the original title. Since the translated title is the same as the original language, it appears blank on TMDB. Therefore, Plex retrieves an empty title from TMDB and falls back to using the Chinese title from IMDB or similar sources. However, IMDB does not support Chinese, so the Chinese title appears in Pinyin format. As a result, Plex fetches the Chinese title in Pinyin format.
