Elasticsearch logs intermittently drop out in Kibana - connection is successful

Issue

• Kibana is showing logs part of the time, but there are gaps that can last for a few hours at a time. These logs never appear. Restarting Elasticsearch and Kibana does not fix the issue, and neither does recreating the Kibana index or deploying a new build.

• Kibana logs show the error:

  {"type":"log","@timestamp":"2019-05-31T14:23:34Z","tags" ["error","elasticsearch","admin"],"pid":225,"message":"Request error, retrying\nPOST https://logging-es:9200/.kibana/_search => socket hang up"}
  

• Kibana returns the error Discover: Bad Gateway