Health check extension shows "Server not available" after adding smartagent/jmx receiver?

[Mironiken]

I am using Splunk Distribution of OpenTelemetry Collector in kubernetes. Current solution is working just fine. But after I added section for the smartagent/jmx receiver with groovy script inside, healthcheck starts to show "Server not available" status.  Groovy script works, logs includes several

2022-11-07T11:12:14.730Z error subproc/core.go:114 Get result, and sent:0 {"kind": "receiver", "name": "smartagent/jmx", "pipeline": "metrics", "monitorID": "smartagentjmx", "monitorType": "jmx", "runnerPID": 42}

(I just added stderr to script)

There are not any other warn/errors in logs. Kubernetes just kills pod cause healthcheck.  My jmx config:

smartagent/jmx:
  type: jmx
  host: 0.0.0.0
  port: 9999
  intervalSeconds: 2
  groovyScript: |
    def printErr = System.err.&println
    ss = util.queryJMX("com.hazelcast:name=MAP_NAME,instance=*,type=IMap").first()
    dims = [env_name: "NAME"]
    output.sendDatapoint(util.makeGauge("hazelcast.map.size", ss.size, dims))
    printErr("Get result, and sent:" + ss.size)

Tell me where and how to dig?