spring-cloud-netflix: ResourceAccessException: I/O error on POST request for : com.netflix.client.ClientException; IOException

Intermittent in production. What would cause this? How best to troubleshoot this? GIVEN versions: com.netflix.ribbon\ribbon-core\2.2.0 - ribbon-core-2.2.0.jar spring-web\4.3.4.RELEASE spring-web-4.3.4.RELEASE.jar There were no errors on the target server related to this time?

org.springframework.web.client.ResourceAccessException: I/O error on POST request for \"": com.netflix.client.ClientException; nested exception is java.io.IOException: com.netflix.client.ClientException
org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:633)\n\tat 
org.springframework.web.client.RestTemplate.execute(RestTemplate.java:595)\n\tat
 org.springframework.web.client.RestTemplate.postForEntity(RestTemplate.java:423)\n\tat
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