dovecot passdb driver=checkpassword as external script for block ip

[bes]

Refer to
https://dovecot.org/pipermail/dovecot/2015-March/099971.html
https://wiki.dovecot.org/PasswordDatabase
I tried to repeat the same thing.
Set these passdb:

passdb {
  args = /myscript.sh ip=%r
  driver = checkpassword
  result_failure = return-fail
  result_success = continue
}
passdb {
  args = /etc/dovecot/dovecot-sql.conf.ext ( my working auth method )
  driver = sql
}

Created executable /myscript.sh:
#!/bin/sh
exit 1

But I saw in the logs:

dovecot[15111]: auth: Error:
checkpassword(techdept at nestormedia.com,192.168.99.128,<Mos6jW94XNzAqGOA>):
Child 15115 exited with status 1
dovecot[18016]: imap-login: Login: user=....[successful login]

Why result_failure=return-fail from first passdb does not work?