A prompt set is throwing an error, when it is used as a Task within a Workflow: Invalid MEMSV handle

Document ID : KB000124517
Last Modified Date : 15/01/2019
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Issue:
A Script (SCRI) Object is executed as the first Task within a Workflow to set initial values. 
The Script uses a Prompt Set, which uses EXEC VARA to retrieve initial user values. 
When the Workflow is executed, it gets stuck in 'Generating' status and the Prompt Set remains in 'Waiting for user input' status. 

A message window displays the following errors: 
U01001002 Invalid MEMSV handle. 
U00015006 System forced memory trace dump 
Environment:
Automation Engine versions 12.0, 12.1 and 12.2
Resolution:
This issue has been found and corrected and will be/is available in the following versions:
Automation Engine 12.0.7 - available 
Automation Engine 12.1.4 - available end January 2019 
Automation Engine 12.2.1 - available 
Automation Engine 12.3.0 - available end February 2019
Workaround: the prompt set should be defined on the workflow level, not child.