For words that have only three letters, there is not any 4th letter. Such as with the word “insert”, there won't be any a lot more letters Later on and so should be the word "insert". The word “addict” is in the BIP39 wordlist however , you might have applied https://linkedbookmarker.com/story4295908/examine-this-report-on-bip39-mnemonic-phrase-tool