Not a nice 20 minutes in Tesco today when their till froze after using a contactless terminal to pay £20 for petrol. My wife was made to feel like a criminal and my grandson sat in the car with me waiting was getting quite upset. The Monzo card app clearly showed the authorisation had gone through but they wanted her to "contact the bank". Well there is no point - the bank updates the app and shows the authorisation.
After 20 minutes I just gave them our name and address and phone number and said we are leaving, and walked out. Happy to pay if the auth times out or is reversed later, but giving my wife grief over their equipment failure is not on!
We shop in Tesco almost every day and on-line. Feeling somewhat cross now.