Had this happen this week at a Tesco Express. The only guy on the register had to call someone out from the back to remove the double-scanned Irn-Bru.

What made it extra awkward was that the staff door was directly down the aisle from the self-checkout, so I could see the employee marching down the aisle so they could deal with this shit and get back to whatever they were doing. I want those 2 minutes of my life back.