Dialog has insufficient privileges

When running a dialog, I receive a "Assignee has insufficient privileges" when the dialog tries to create a new custom record against an opportunity owned by another user.  (detailed log is below).  

The thing that has me confused is that I am a Sys Admin, and the dialog does not have settings to change "run as" that a workflow does.

Why would a dialog run by a sys admin have insufficient privileges?

Many thanks for your help!

Rob

Error Details:

Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: Principal user (Id=c2faaa84-7874-e611-80eb-00155df17501, type=8) is missing prvReadnew_stakeholders privilege (Id=56c42047-492d-469a-8cbf-6654822ce0af)Detail:
<OrganizationServiceFault xmlns:i="www.w3.org/.../XMLSchema-instance" xmlns="schemas.microsoft.com/.../Contracts">
  <ActivityId>e202d0cf-6602-4875-900d-539991394840</ActivityId>
  <ErrorCode>-2147220943</ErrorCode>
  <ErrorDetails xmlns:d2p1="schemas.datacontract.org/.../System.Collections.Generic" />
  <Message>Principal user (Id=c2faaa84-7874-e611-80eb-00155df17501, type=8) is missing prvReadnew_stakeholders privilege (Id=56c42047-492d-469a-8cbf-6654822ce0af)</Message>
  <Timestamp>2018-04-18T21:46:56.7805985Z</Timestamp>
  <ExceptionRetriable>false</ExceptionRetriable>
  <ExceptionSource i:nil="true" />
  <InnerFault i:nil="true" />
  <OriginalException i:nil="true" />
  <TraceText>
[Microsoft.Xrm.Sdk.Workflow: Microsoft.Xrm.Sdk.Workflow.Activities.CreateEntity]
[CreateStep19: Create stakeholder record]

</TraceText>
</OrganizationServiceFault>