For words that have only 3 letters, there is not any 4th letter. Such as with the word “insert”, there are no extra letters afterwards and thus have to be the word "include". The word “addict” is during the BIP39 wordlist however you might have applied “addi” for “addict”. If https://mirrorbookmarks.com/story18740616/top-guidelines-of-bip39-word-list-pdf