Our system has DWA (Direct Web Access) assignment implementation which enable the company external clients to submit their task even without access to the site. 

Problem is, we have an activity that sets the Task Assigned to field to the worklist/workbasket of the priority task. We want to call it in the pre-load activity as this is the same implementation with authenticated user. The activity is displaying Access Denied - This request for information cannot be processed (Session state is invalid) when calling the activity on the pre-load of a container. This container is in the Perform External Harness.

Is this expected for a DWA (Direct Web Access) or if not can someone help me how to achieve this? 

Thanks in advance.