Set ACL merge mode to ROLES
Create a series where the Non-Admin has read & write rights (easiest if it is created by the Non-Admin)
Let an Admin create an event belonging to that series (no publishing necessary)
When the workflow is finished, delete everything belonging to the media package from the Workspace and Working File Repository
Try to delete the event with the Non-Admin - the user should have the necessary rights, but the media package in the workflow instance still points at the WFR, where the ACL cannot be found, so the workflow cannot be deleted and the event deletion fails.