Fluentd logs "Fluent::ElasticsearchOutput::ConnectionFailure" error="Can not reach Elasticsearch cluster" in OCP 3.11

Issue

• Kibana fails with below error:

Discover: [exception] The index returned an empty result. You can use the Time Picker to change the time filter or select a higher time interval
Error: [exception] The index returned an empty result. You can use the Time Picker to change the time filter or select a higher time interval
    at respond (https://kibana.example.com/bundles/kibana.bundle.js?v=15690:12:2730)
    at checkRespForFailure (https://kibana.example.com/bundles/kibana.bundle.js?v=15690:12:1959)
    at https://kibana.example.com/bundles/kibana.bundle.js?v=15690:1:9184

• Fluentd logs show below error:

Fluent::ElasticsearchOutput::ConnectionFailure" error="Can not reach Elasticsearch cluster

• Elasticsearch health is GREEN, without any Unassigned shards but the logs show:

[WARN ][r.suppressed             ] path: /.operations.*/_field_stats, params: {level=indices, index=.operations.*}
org.elasticsearch.ElasticsearchException: The index returned an empty result. You can use the Time Picker to change the time filter or select a higher time interval
        at io.fabric8.elasticsearch.plugin.filter.FieldStatsResponseFilter$1.onResponse(FieldStatsResponseFilter.java:71) [openshift-elasticsearch-plugin-5.6.16.1-redhat-1.jar:?]