Can you help me with the following error from my indexers?: "SID s already running"

[jhall0007]

Hello All,

I am occasionally seeing this error from my indexers. Has anyone else seen it?

ERROR StreamSearch - sid=remote_$host$_subsearch_tmp_1539964969.4, A search with sid=remote_$host$_subsearch_tmp_1539964969.4 is already running

I'm running Splunk 7.1.3, ES 5.1.0, RHEL, single non-clustered search head hitting multiple indexers. I am troubleshooting an issue where occasionally there will be a search error showing an indexer did not respond to a search request.

Thanks.