For words that have only 3 letters, there's no 4th letter. Such as with the word “insert”, there are no a lot more letters afterwards and thus needs to be the word "add". The word “addict” is during the BIP39 wordlist however you would have made use of “addi” for https://opensocialfactory.com/story19950089/examine-this-report-on-bip39-passphrase