For words that only have 3 letters, there isn't any 4th letter. One example is with the word “include”, there isn't any much more letters afterwards and thus needs to be the word "increase". The word “addict” is from the BIP39 wordlist but you might have employed “addi” for “addict”. https://highkeysocial.com/story4527372/5-essential-elements-for-bip39-explained