Jenkins validates the JMeter build as successful when it’s actually failed

Set "Use error thresholds on single build" from 0 to 1.

This should mean that the jenkins build fails if at least 1 error is in your JMeter test case, where a 0 ignores the error count (If I remember this correctly).

Sounds like a Performance Plugin issue, I believe you should report it via Jenkins Bug Tracker

In the meantime to work this around I would suggest returning non-zero exit code for the JMeter build step, the fastest and the easiest way is running your JMeter test using Taurus tool as a wrapper. Taurus has powerful Pass/Fail Criteria subsystem where you can define the conditions of your build failure. If the condition will be met Taurus execution step will be finished with code 3. Jenkins is smart enough to automatically fail command-line tasks with non-zero exit code.

Minimal working Taurus config file:

---execution:  scenario: my-testscenarios:  my-test:    script: C:\Users\maria\Desktop\Automation\WIP\Test-page.jmxservices:- module: passfail  criteria:  - succ<100%, stop as failed

More information, if needed: Meetup Recap on Using Taurus to Automate JMeter and Jenkins Tests

You can also change JMeter exit code directly form the JMeter test via i.e. JSR223 Scripting Elements like:

if (some condition) {    System.exit(1);}

but in this case you won't have much flexibility in terms of setting failure criteria

I set my Select evaluation mode to standard mode, Set the radio button on Error Threshold and set Unstable and Failed to 1