SharePoint 2013 Error: Unexpected response from server. The status code of response is '500'. The status text of response is 'System.ServiceModel.ServiceActivationException'.

SharePoint 2013 Search returned an error:
Unexpected response from server. The status code of response is '500'. The status text of response is 'System.ServiceModel.ServiceActivationException'.


In Event logs of SharePoint web front ends, it left an event:
System.ServiceModel.ServiceHostingEnvironment+HostingManager/33228940
Exception: System.ServiceModel.ServiceActivationException: The service '/_vti_bin/client.svc' cannot be activated due to an exception during compilation.


Solution: 
Either increase the Server Memory or Try closing some running applications in the SharePoint WFEs to freed up the memory in server!

You can also try limiting the memory consumption on various services running on the server. Here are some:

• Limit the search service 

• Set-SPEnterpriseSearchService -PerformanceLevel Reduced 

• Limit the NodeRunner.exe's memory (NodeRunner is a SharePoint Search component)
• Open the configuration file at "C\Program Files\Microsoft Office Servers\15.0\Search\Runtime\1.0\noderunner.exe.config" Locate the node "nodeRunnerSettings" and set the value for "memoryLimitMegabytes" attribute. By default its value is 0 (which means unlimited). Once done, restart SharePoint Search Host Controller process.

It also happens with you try add/update new items to SharePoint 2013 lists: