@thegibson i have 2

once i broke diagnosis history tracking in a large medical record system and the bug made it to production ; they lost 3 months of diagnostic history summaries due to the bug (this is v. bad for those not in healthcare)

one day i got a panicked phone call from a customer because the 'fix' i had just deployed to production broke /all/ medication dispense data entry in the system ; the entire nursing staff had to cancel their appointments for the day