I have a site workflow:
This site workflow is triggered manually. This creates a text file and put the text file in the Shared Documents Library.
The site collection has only 3 owners from which one has created the WF and receives "403: Forbbiden" and one can run the WF without "403: Forbidden."
SharePoint administrator and Global administrator + rest of the WF creator TEAM receive this "403:Forbbiden" into the Workflow Status after we run it.
The same applies to 2 other Nintex WF`s in this site collection.