Intermittent empty transcriptLanguages in /v1/metadata for YouTube

The `transcriptLanguages` field in the `/v1/metadata` endpoint is returning intermittent results for YouTube URLs (e.g., https://www.youtube.com/watch?v=L5anUhwF9dc). Sometimes it returns the correct languages (e.g., `["es"]`), and other times it returns an empty array `[]` for the same video. This is affecting production workflows where the user cannot switch to deprecated endpoints. The user expects consistent detection of available transcripts.