1988605 - Error 'WilyHostService is not available' in substep 'Introscope Host Adapter' for BOE or Tomcat managed system

The following error occurs in the step 'Introscope Host Adapter' for BOE or Tomcat managed system

On instance : <hostname>/<instance>
Connection to SMDAgent <hostname> could not be established!
Reason: Smd agent Service 'Implementation as null of object
entities:com.sap.smd.agent.application.wilyhost.WilyHostService is not
available' not available.

Also, the following errors appears in the SMDAgentApplication.X.log which locates in the 'log' folder under the installation path of Diagnostics Agent:

com.sap.smd.wily.hostagent.WilyHostService - init(...): Failed to start Agent!
[EXCEPTION]
 java.rmi.RemoteException: WilyHostAgent start failed; nested
exception is:     com.sap.smd.wily.hostagent.PermanentException:
com.sap.engine.lib.xml.parser.NestedSAXParserException: Fatal Error:
com.sap.engine.lib.xml.parser.ParserException: XMLParser: Bad
attribute list. Expected WhiteSpace, / or >:(:main:, row:1,
col:177)(:main:, row=1, col=177) ->
com.sap.engine.lib.xml.parser.ParserException: XMLParser: Bad
attribute list. Expected WhiteSpace, / or >:(:main:, row:1, col:177) 

SAP Solution Manager 7.1

KBA , SV-SMG-DIA-SRV-AGT , Agent Framework , Problem