Staff and patron are different users of the library. Within the system their differences are set in terms of permissions (of use, access, modification etc). Students and non-librarian staff (i.e. GRA and SI employees) are generally registered as ‘Patrons’. When a new user account is created for a librarian, we usually set it as ‘Global Administrator’.
Currently all librarians and working-students have the same permission profile (the system administrators too!). This could be changed (different profiles are available, like cataloguer, local administrator etc) but so far there has never been an issue. Individual permissions can be modified in Administration > User Permissions Editor, although this is normally not necessary if the user profile is set correctly. See Permission Editor for more info on this.
In case of overlaps or errors in the creation of User Accounts, they can be deleted from within the Patron Editor, clicking Other > Completely Purge Account.
It can happen that sometimes users are double imported due to redundancy in the Rietveld system, or there is an overlap as the barcode has been spelled wrong or something, so they end up having two different barcodes.. In that case one of the two gets deactivated! Which means the user cannot borrow books, as the Check-Out function is greyed out.
You can fix it by going to the Patron Edit page, and next to the first element, Barcode, you can click on the See All button. In the dialog you can turn both barcodes active again, or otherwise fix the wrongly spelled barcode.