Pipeline: Groovy 4030.v7c3a_975886a_8 introduced a warning for forgotten def keywords (related PR). After the update those entries appeared in the build logs. However, even a minimal Pipelines prints them multiple times:

Did you forget the `def` keyword? WorkflowScript seems to be setting a field named delegate (to a value of type WorkflowScript) which could lead to memory leaks or other issues.
Did you forget the `def` keyword? WorkflowScript seems to be setting a field named resolveStrategy (to a value of type Integer) which could lead to memory leaks or other issues.

Example to reproduce:

pipeline {
    agent any

    stages {
        stage("Test") {
            steps {
                echo("ABC")
            }
        }
    }
}

Here the message above appears twice: after "Start of Pipeline" and "Stage (Test)".

There are warnings regarding delegate and resolveStrategy on all pipelines, but there's no hint how / what to fix, nor are they user written.