In Events Manager 5.3 it's not possible to set a user whose role is a Subscriber as the author of an event, neither a normal or a recurring one, or a location. The dropdown list of users who can be set as the author contains only users with the user level of Contributor or above.
In EM settings the Subscribers can immediately publish normal and recurring events and locations so it's rather strange that they can't be set as event authors by an admin.
The proper fix is to list all the users in this list, regardless of the role. First, admins should have the total administrative power (no one else should be even able to see that option in the UI), and second, when there's an [event_form] page, anyone can submit an event regardless of their user role and get it accepted by a moderator, making them authors of a published event. It'd be odd for an admin to not be able to eg. recreate an overlong event as a recurring one, delete the old single event and mark the recurring one as owned by the same user so they can update it as necessary.