Whenever you archive a tweet, you only get that tweet (thanks a lot, Musk), and nothing else. Example:
https://x.com/SurreyPolice/status/1863903221502099944
Strangely enough, you can solve that by replacing the username, in this case SurreyPolice, with 'i'. Then it will apparently use a logged in browing session to archive, and you will get at least more. So:
https://x.com/i/status/1863903221502099944
That will make the archive look like:
Might be worth informing the folks over on Nitter's GitHub. There is still an active discussion on accessing how to access tweets from a logged in session without needing to have a farm of accounts that can be taken down at any time.