For words that only have three letters, there is not any 4th letter. Such as with the word “insert”, there won't be any additional letters afterwards and thus should be the word "add". The word “addict” is during the BIP39 wordlist however, you might have utilised “addi” for “addict”. bip39-phrase.com https://postheaven.net/tiablexcen/mastering-your-copyright-protection-the-essential-overview-to-bip39-passphrases