I’m curious if the system being confusing, annoying, and not notifying you if you made a mistake is enough of an excuse to get out of this. I know I’ve been really frustrated by self-checkout (and hence never use them if I have a choice, unless I’m checking out with like one item), and I’m a pretty intelligent and technologically advanced person. I can see plenty of accidents happening with people walking about without having paid for something. This could add up fairly quickly. Is it still illegal if it’s because of choices the store made?

That’s total, not per trip. They can still add up all of your trips if they have the evidence.