To recreate: 1 - Define a patron category, say Juvenile, as "Can be guarantee" 2 - Find a patron in Juvenile category and assign a guarantor from Patron category 3 - Update Patron category as "Can be guarantee" 4 - View Juvenile patron, no warning 5 - Edit patron, see warning "A guarantor cannot be a guarantee." 5 - Enable "TrackLastPatronActivityTriggers" for checkin and checkout 6 - Checkout an item to the Juvenile, KO, "Child patron cannot be a guarantor." 7 - Checkin the item "Child patron cannot be a guarantor." In KTD we get a stack trace, in production we were seeing an error "Item not checked in. Check the about page (Child patron cannot be a guarantor.) We should add a warning on the child patrons details and checkout screen, and possibly add a test on the about page Possibly we should not allow the category to be updated if any existing patrons are guarantors already