SharePoint 2013: Microsoft.Office.Server.Search.Administration.ISearchServiceApplication], cannot be used for communication because it is in the Faulted state

Problem

A few users report that when they connect to pages containing Content Search web parts, the web part displays: Sorry, something went wrong.  When the VIEW DETAILS link is clicked, these users sees this:

The communication object, System.ServiceModel.Configuration.ConfigurationChannelFactory`1[Microsoft.Office.Server.Search.Administration.ISearchServiceApplication], cannot be used for communication because it is in the Faulted state.
Correlation ID: 00000000-0000-0000-0000-000000000000

Most other users report that when they navigate to such pages, the Content Search web part displays content as expected.  Below is my investigative method to resolve this issue.
  

Troubleshooting

1. Facts
1. A single user experiences the issue
2. Farm employs Windows network load balanced: WFE1 + WFE2, where WFE1 has priority
3. One Application server
4. SharePoint 2013 farm is patched through July 2015
5. All Windows Server 2012 are patched through July 2015
2. Findings
1. Verified user experience: user was able to reproduce issue.
2. Could not reproduce issue from administrator workstation.
3. Ad hoc selection of other users could also not reproduce user issue.
4. Windows Server Services: Search services running on both WFE1, WFE2
5. SharePoint Services on Server: Search services running on both WFE1, WFE2
6. SharePoint Search Administration: all search components up and running (green checks)
7. IIS: all sites and application pools started on both WFE1 and WFE2
8. Able to reproduce issue by logging into WFE2 and then connecting to the page.
9. ULS Logs: instances of the error message (presented above) was found in the ULS logs for WFE2 only.
3. Research
1. Found a posting, Unable to search Document Library, suggesting search component service restart and IIS restart to resolve similar problem.
4. Testing
1. Restart the Windows Server services SharePoint Search Host Controller and SharePoint Server Search 15: issue still presents on WFE2.
2. Restart the SharePoint Server service Search Query and Site Settings Service on WFE2: connecting to page on WFE2 returns HTTP 500.
3. Perform IISRESET on WFE2: connecting to page, while logged into WFE2, Content Search web part now displays content as expected.

Solution

1. Identify that server hosting the problematic Search service
2. In Central Administration > Services on Server, restart Search Query and Site Setting Service on the server.
3. On that server, perform IISRESET.

References

• ISearchServiceApplication interface
• Unable to search Document Library