I would like to suggest that when you list the characteristics for a password for the Vault that you list the maximum password length in addition to the minimum length. In addition, if the new password entered is too long let the person know that you are ignoring any characters after 20.
I ran into a problem today when I updated my Vault password. I entered a 23 character password. (I use this number since it allows me to create 4 groups of 5 characters each with a hyphen between each group.) When I did that today, the Vault's password change screen accepted my new password and the confirmation when I reentered it. However, the next time I went to log in, I was told the password that I entered was wrong. I then had no choice but to delete my vault.
In creating a new Vault later, I realized that the Vault ignores any characters typed after 20 when the password is being created as well as doing the same thing when it is re-entered to confirm. However, it then rejects the password when you later sign in if it is longer than 20 even if the first 20 characters entered are correct. (I didn't realize the problem the first time since the Vault by default doesn't show the characters being entered. I only realized it when I had the Vault show me what it had entered.)