It's a common sight at many retail stores: a queue of people, waiting to use a self-checkout kiosk, doing their best to remain patient as a lone store worker attends to multiple malfunctioning machines.
I have never had this happen. The only issues I've ever had is people not understanding something so simple as scanning a barcode and then tap to pay.
Self checkout is one of the greatest advancements I've ever had. Probably the most irritating thing about California is that they made it illegal to use a self checkout to buy beer. The state literally forced me to stand in lines when i can easily scan a barcode.