Occurred on April 7, 2019 / Brisbane, Queensland, Australia
Info from Licensor: "We found out the McDonald's kiosk machine had a loophole where you could order a dollar burger, and then remove the patty that was worth $1.10, resulting in pattyless burgers for -10 cents each. If we bought 10 of these and then one regular dollar burger, this resulted in an order that was free."