Update Field Workflow Task sets user to Adminstrator

This happens on demo.vtiger.com.

I created a test user in a non-admin role.

I created a simple Workflow on Leads that used the Update Field Task and an Expression to populate the Annual Usage field with a number based on the the value of the lastname field.

When I log in as this non-admin user and trigger the workflow, it updates the field, but sets the user on ModTracker (the Updates tab) to say "Adminstrator".

I then changed it to use Raw Text rather than an Expression. It again populated the field, but set the Updates user to Administrator.

I then changed it again to populate the field using another field as the source. Same thing happened.

Then I deleted the workflow and edited a field using the same user. This time the user recorded in the Updates is correct.

See attached screenshot.

All changes shown below (apart from the initial creation) were made by the same user "demo demo" who was a non-admin user in the Sales Manager Role.