For words that have only three letters, there is not any 4th letter. For example with the word “add”, there isn't any extra letters afterwards and therefore should be the word "insert". The word “addict” is within the BIP39 wordlist but you might have employed “addi” for “addict”. Mnemonic words https://cyberbookmarking.com/story18916912/considerations-to-know-about-bip39-seed-phrase-generator