Change OSX encryption filevault password to match login pass
Just bumped into this issue too, if you change password via 


  Settings > Users &amp; Groups > Change Password ...


you will be prompted twice, once for the File Vault original password and again for the new account password.  However if you change the password via 


  Settings > Security &amp; Privacy > Change Password ...


both will be updated, noting that you will be required to enter the account password not the File Vault original password, so you can reset the File Vault password by entering your new password three times.