I am running Jenkins on GKE, migrating from VM. I am getting this error in one of the gradlew test builds. Anyone has any idea on how to approach it?

Error when executing always post condition:
java.lang.IllegalArgumentException: Could not instantiate {delegate={$class=Publisher, reportFilenamePattern=**/testng-results.xml}} for org.jenkinsci.plugins.workflow.steps.CoreStep: java.lang.UnsupportedOperationException: no known implementation of interface jenkins.tasks.SimpleBuildStep is named Publisher


Caused by: java.lang.UnsupportedOperationException: no known implementation of interface jenkins.tasks.SimpleBuildStep is named Publisher