Symptoms

Workflow Task State of a form not getting its associated SP list item ID passed in when tying the 'On Form Submit' trigger to a non-default button. Error on 'Open the Worklist Item" rule: "SmartObject property ID is a required property for selected method GetListItem. Value must be set."
 

Diagnoses

'On Form Submit' trigger passes the value correctly to the default 'Save' button on the generated 'New' form, but not when this button is recreated elsewhere.
 

Resolution

As a workaround, we did not delete the default button but hid it and called it via a 'Execute another rule" rule tied to a button on the Form level. Resolved the issue by passing back the ID to the SmartObject reference in the Output Mappings of the Create List Item method in the new button.