Comment by stephen_g

I've noticed at supermarkets here that of the dozens of times those 'you haven't scanned something' warnings have come up, only one time the item hadn't actually scanned when I thought it had. Every other time has been a false positive for me. They're pretty dodgy, the workers always seem pretty frustrated with it as they go around clearing them for people (sometimes a handful of people waiting, falsely accused by the machines)...