For words that only have three letters, there's no 4th letter. For example with the word “insert”, there are no extra letters afterwards and so need to be the word "add". The word “addict” is from the BIP39 wordlist but you might have utilized “addi” for “addict”. The use of https://livebookmarking.com/story18784806/fascination-about-bip39-english-words