For words that have only three letters, there's no 4th letter. For instance with the word “insert”, there won't be any more letters afterwards and therefore should be the word "increase". The word “addict” is from the BIP39 wordlist however you might have used “addi” for “addict”. This extra complexity https://bookmarkboom.com/story18919281/the-fact-about-bip39-seed-phrase-word-list-that-no-one-is-suggesting