For words that have only three letters, there is absolutely no 4th letter. Such as with the word “include”, there aren't any additional letters afterwards and therefore needs to be the word "insert". The word “addict” is within the BIP39 wordlist however, you would have applied “addi” for “addict”. Meticulously https://bookmarklethq.com/story18766855/the-fact-about-valid-bip39-seed-phrase-that-no-one-is-suggesting