Unexpected item in the bagging area...

Using these machines can be such a mundanely perverse experience. The screen prompts you to put your shopping bag on the appropriate surface. Then it finds the bag unacceptable in some undefined way, and the summoned human being never appears (no doubt staffing levels are a bit low). Sigh.
I read an article somewhere yesterday - I think it was about mental health and loneliness - and it mentioned survey evidence showing that many customers prefer staffed tills to these self-service machines. Even if it means that queues move more slowly. Well, no shit Sherlock...