Getting error as "Error: "Project Number" can not be the new parent to child" when users trying to create a child project task under a project task.Issue Getting error as "Error: "Project Number" can not be the new parent to child" when users trying to create a child project task under a project task.ResolutionUpon investigation by our Development team, it was found that this is related to known Problem PRB714717.Essentially, the Business Rule's evaluation of condition (a field changed) is getting evaluated as true on fields that aren't really changed, this is getting replicated with reference fields as well in addition to DateTime fields as specified in the above PRB. As a workaround, our Developement team has stated that we can add an extra condition check to the "Validate change parent" Business Rule. To apply the workaround, follow the steps below. NEXT STEPS: 1. Navigate to System Definition > Business Rules2. In the "Name" column search for "Validate change parent" and go to the record3. Go the the Advanced tab4. Change the Condtion field to: (current.instanceOf("pm_project") || current.instanceOf("pm_project_task")) && ( current.parent != previous.parent) 5. Save the form