For words that only have three letters, there is not any 4th letter. Such as with the word “insert”, there are no far more letters afterwards and thus must be the word "increase". The word “addict” is during the BIP39 wordlist however, you might have applied “addi” for “addict”. Another https://meshbookmarks.com/story19090813/the-fact-about-bip39-seed-phrase-word-list-that-no-one-is-suggesting