Unable to reassign Journey tasks to external employees

Summary:

We are not able to reassign tasks in Journeys page to external employees (Contingent worker/ETL). However, we are able to search them via employment info and person management.

What could be the issue since it doesnot look like an access issue as the external employees are searchable in other pages. Only when we try to click on reassign and search for the external employee, the employee's name doesnot come up.

Please advise.

Mayurika