For words that have only 3 letters, there isn't any 4th letter. For instance with the word “insert”, there are no more letters afterwards and therefore need to be the word "increase". The word “addict” is within the BIP39 wordlist however, you might have utilized “addi” for “addict”. Standard recovery https://bookmarkstown.com/story19041907/detailed-notes-on-copyright-wallet-seed-phrase-out-of-bip39