For words that have only 3 letters, there's no 4th letter. For example with the word “insert”, there aren't any a lot more letters afterwards and so has to be the word "add". The word “addict” is inside the BIP39 wordlist but you would've utilised “addi” for “addict”. Meticulously evaluation https://e-bookmarks.com/story4417061/the-invalid-bip39-phrase-diaries