This is a project request site workflow that results in a document set being created within a library. The initiation form collects information such as project name, project sponsor, description, etc. The form has not been customized with IP or Nintex forms. The Project Sponsor column is of type Person or Group in the form and the document library.
When running the workflow, the following error is generated:
Failed to create item. Invalid data has been used to update the list item. The field you are trying to update may be read only.
The workflow runs as expected when removing this field from the Create Item action. The workflow also runs as expected if I add an Update Item action immediately following the Create Item action. In the Update Item action, I rely on the same workflow variable captured in the initiation form and write to the same column in the document library. This workflow completes with expected results. So fortunately there's an easy and acceptable work-around. But it's definitely a bug.