It sounds like the weird symbol is a post-processing error. Can you check the file contents outside of your csv viewer?
If you are seeing truncated Tweets, it’s likely they were from a standard endpoint without using the tweet_mode=extended setting. This parameter must be used in order to get the full text after 140 if it’s a longer Tweet.
When you say ‘the archive’ I’m not sure what you mean, but we do have a Search Tweet FullArchive endpoint that would return the full Tweet text and more metadata than the standard endpoints by default.