The commentThreads endpoint with videoId is experiencing multiple issues (YouTube API v3).
If you use the parameter maxResults=100, it returns only 20 (the default) items. It seems that the endpoint is currently not using that parameter, issues started today.
Also not all comments in total seems to be returning by this endpoint for paginated requests for multiple issues. I assume this is related, but could be also another issue.
Example request: https://www.googleapis.com/youtube/v3/commentThreads?part=snippet&maxResults=100&videoId=LkpZ3qKLrsQ&key={api-key}
Expected comments (data.items) in response: 77Actually comments (data.items): 20 (the default maxResults) with a nextPageToken provided
For the other issue you can use the same request with videoId wqW5vgARg4k and following the pagination by adding pageToken={nextPageToken from previous request}.It is only returning 292 (484 with replies) comments, but should return 22596 comments.