Sainsbury's have the worst self-service checkouts IMO
I thought Sainsbury's branded themselves as one of the 'better' supermarkets but the self-service checkouts at my local store are awful. They constantly find faults, and require checking by an assistant because the computer isn't weighing things correctly or god knows what.
Then when you try to leave, you are locked in and have to scan your receipt - which you weren't told to do at the start, so if you haven't printed a receipt you have an akward argument with the assistant, trying to prove you did pay actually, and who hates you because they have already been over to enter their pin number sixteen times at your checkout!
I just don't go in to Sainsury's anymore! I'd rather spend my life savings in Waitrose, keep my dignity, and not be treated like a criminal