I have just configured some jobs to send emails on "Failure - 2nd" and "Fixed".
The behavior I'm seeing is that if the job has ever failed in the past, then the "Failure - 2nd" email gets sent on every subsequent build, even if the build is successful.
Here's the output I see in Jenkins:
The expected behavior, according to the plugin doc, is that it would only be sent on successive failures. Note that this build is neither a failure, nor a successive failure.