Like most JIRA setups, we have the "atlassian-addons-project-access" project role that has the ability to Administer Projects. Somehow, many users have this project role and therefore can administer the project.
Using the "People" section of the Project Settings, I can add and remove roles, however, the atlassian-addons-project-access project role is missing.
In addition, when I explore the role to see members, it says 0 members, however, via the permissions helper, it reveals that users have the Administer Projects permission via the atlassian-addons-project-access project role.
A tangled web...
Thanks for the help
Ryan