When using a new segmentation task to populate an engagement factor field previously populated by a different task, you may see the engagement factor fields for constituents that do not meet the criteria for new task not be cleared out.
We are currently evaluating this issue and will update this article when we have more information.
Steps to Duplicate
Create a new Segmentation Task (Web Site Usage or Email Response) and map to an engagement factor field
Run the task to populate the engagement factor field
Check results on constituents
Create a new task and map to the same engagement factor field
Run the task to populate the field based on new criteria