@sandeepm744005 Were you guys able to determine the root cause for this issue? Any pointers you would like to share with us? We are also having the same heap dump leak suspects that you have mentioned above.

@anuj_pathak1 Were you able to resolve this bug with OOTB Workflow template not honoring the externalizer domain mapping? We are implementing this for one of the projects and need no customization of templates and unfortunately it doesn't work fine even in AEM 6.5.4.  Any pointers would be helpful!