I keep seeing the following error message in my ECK cluster:
[buyerportal-0 buyerportal] {"log.level":"error","@timestamp":"2023-05-19T06:46:40.752Z","log":{"logger":"elastic-apm-node"},"ecs":{"version":"1.6.0"},"message":"APM Server transport error (503): Unexpected APM Server response when polling config\nAgent configuration infrastructure is not ready. Please retry later."}
Kibana version: 8.7.1
Elasticsearch version: 8.7.1
APM Server version: 8.7.1
What's the root cause? How to resolve it?