Sainsbury's self service tills never work properly. I never get problems with the self service tills in Asda, Waitrose or M&S, but if I use the ones in Sainsbury's, I have to call an assistant sometimes as much as 3 times because the machine doesn't register the goods properly.
It starts off by requesting that if you have your own bags, you place them in the bagging area and press "Start". As soon as I do that, before I begin putting any items through, the machine announces "Unexpected item in the bagging area"...... and I have to call the assistant. And so it goes on.
If other supermarkets can have quick and easy checkouts that don't have all these hiccups, why can't Sainsbury's?