There is a grocery store about 2 miles from my house that will freak out if you look at it funny. I gave up one day, the helper person came back for the 3rd or 4th time to unstuck the "self"-checkout in my ~20 item shop. I told them they can just cancel the transaction and walked out. I now go to the grocery store 8 miles away, that always has at least 1 human cashier open in addition to their self-checkout lanes. I rarely use the self-checkout because they are the ones that are only useful for a handful of items, but I've never had it give me a problem.