Reset Scenario Error: Error processing data. The item was not found. Entity, Parent, -1.

You are correct that this error normally indicates a Entity member who has an invalid Parent Relationship.  

You could run the following to help identify what entity member is causing this:

1. Create a new data adapter within the Application Workspaces
2. Set the Data Adapter to a SQL Data Adapter and use the Application as the database location and use the following query:

select * from Relationship where ParentID = '-1' and DimTypeID = '0'

This should return the rows of any relationships that do not have parent records for the entity dimension

The MemberID will be the 'ChildID' column 

Then you can query the member table to see the dimension members based on the dimension IDs that are returned

select * from member where DimTypeId = '0' and MemberID = '<ChildID>'

That should help you identify what entity members are causing the issue.

You may have a workflow that is referencing an entity that no longer exists or doesn't resolve correctly, and the Reset is attempting to clear it and not finding the parent member referenced.

Hope this is helpful for you.