ServiceNow - Demand management: inserting tasks creating blank updates on the activity trail on the parent demand

the Business Case, Nature of Demand, Start Date and Target Delivery Date fields are getting updated are showing as updated in the activity trail whenever a new demand task is created

 Whilst we couldn't reproduce it on the OOTB PDi, we noted that this issue was being caused by OOTB scripts in our environment:

- business rule: "Rollup Demand  Actual Effort"

- script include: "DemandEffortUtil"

How we fixed it

we referred the issue to ServiceNow Support, but in the meantime added a line of code to the business rule as follows which appears to have resolved the issue

if (current.operation() == 'insert' && JSUtil.notNil(current.parent) && !current.work_effort.nil())

(update: it appears a custom asynch business rule on worknotes on the demand table was the culprit)