For words that only have three letters, there isn't a 4th letter. For instance with the word “incorporate”, there isn't any more letters Later on and thus needs to be the word "increase". The word “addict” is while in the BIP39 wordlist but you might have used “addi” for “addict”. https://tornadosocial.com/story4344078/a-review-of-bip39-phrase-list