For words that have only three letters, there is no 4th letter. Such as with the word “increase”, there isn't any far more letters Later on and thus needs to be the word "insert". The word “addict” is inside the BIP39 wordlist but you might have used “addi” for “addict”. https://toplistar.com/story20668183/the-greatest-guide-to-seed-phrase-bip39