For words that have only three letters, there isn't a 4th letter. Such as with the word “insert”, there won't be any far more letters Later on and therefore should be the word "increase". The word “addict” is inside the BIP39 wordlist but you might have made use of “addi” https://bookmarkwuzz.com/story18859407/the-2-minute-rule-for-bip39-all-words