For words that only have 3 letters, there's no 4th letter. Such as with the word “insert”, there isn't any additional letters Later on and therefore have to be the word "include". The word “addict” is during the BIP39 wordlist however , you might have utilised “addi” for “addict”. Mnemonic https://bookmarkspy.com/story21051605/fascination-about-invalid-bip39-phrase