Error while parsing PI response (HTTP status code 200 received, but an error occurred while parsing the responce. No XI response received.)

Hello,

This error seems common but somehow no information out there could help resolve it so I decided to start a new discussion and I intend when this gets eventually resolved to post a step by step checklist to help resolve the error. I have tried several ways, checked my error log, adapter configuration, design objects in ESR, Configuration Scenarios in Integration Director; It all seems fine. My PI version is 7.4 dual stack.

Common suggestions have been;

1. 1. Restart the PI Server
2. 2. Check the Channel monitor, in our case the channel is active and green but after a service test in WS Navigator fails it tunes red. Same thing happens using SOAPUI.
3. 3. Make a change in in the Communication Channel ans active again
4. 4. Check CTA cache and configuration

The error from WS Navigator is:

Web service returned error. Fault Code: "(http://schemas.xmlsoap.org/soap/envelope/)Server" Fault String: "Server Error"

<SOAP:Envelope xmlns:SOAP='http://schemas.xmlsoap.org/soap/envelope/'>

  <SOAP:Body>

    <SOAP:Fault>

      <faultcode>SOAP:Server</faultcode>

      <faultstring>Server Error</faultstring>

      <detail>

        <s:SystemError xmlns:s='http://sap.com/xi/WebService/xi2.0'>

<context>XIAdapter</context>

<code>ADAPTER.JAVA_EXCEPTION</code>

          <text><![CDATA[

1. com.sap.engine.interfaces.messaging.api.exception.MessagingException: com.sap.engine.interfaces.messaging.api.exception.MessagingException: XIAdapter:SYSTEM_FAILURE_INTERNAL::::::An internal error has occurred

  at com.sap.aii.adapter.soap.web.SOAPHandler.processSOAPtoXMB(SOAPHandler.java:746)

  at com.sap.aii.adapter.soap.web.MessageServlet.doPost(MessageServlet.java:530)

The Message Monitor error log is: 

Error while parsing PI response (HTTP status code 200 received, but an error occurred while parsing the responce. No XI response received.)

Error Category :     XI_J2EE_ADAPTER_XI_HANDLER

Error Code       :     ERROR_PARSING_PI_RESPONSE

Quality of Service  BE

The Trace Log Viewer error is:

This is a major setback, any suggestions to help resolve the error will be highly appreciated. I hope someone has come across this error in this forum before.