Update Child Contacts gallery custom function ERROR

Update Child Contacts gallery custom function ERROR

I am trying to use a custom function from the Zoho Gallery and I am getting the following error:


Execution Failed
Error details:
Error in executing Mass_update_of_Child_Contacts workflow.
Error.
Error in executing Set Variable task. Unable to update template variable rec.
Error evaluating MAP expression :

Any ideas?  Is it the function or the workflow that is the problem?
Thanks,
Kristin