What happens if you fail a scan and shop check?

We don’t use it anymore but we used to in Waitrose when it was launched a few years ago. Couple of interesting things about our experience on keep getting these ‘random’ checks. On the flip side, I did get the chance to grill the manager endlessly on what was going on whilst constantly being flagged for checks! We initially probably did get a random check, all was good, inconvenienced definitely - because the whole point is it’s supposed to cut down on till time and when you’re checked, you’ve got to unpack it all and go to a till which is a massive pain blah blah blah. Then on the second occasion I was rolling my eyes and impatient so started asking questions and the manager explained (by bringing up all our past purchases on screen) that we’d probably been picked because we HADN’T bought something we usually buy. By ‘usually buy’, I’m talking a consistent purchase for a good few weeks and then no purchase (it was some sort of booze, not mega expensive, maybe like £12 or something). Basically, the algorithm was using our ‘shopping habits’ to request a check to see if you really didn’t buy this product that you have historically bought week after week. Obviously, this needs a human to verify it isn’t sat in your trolley, scanned and ostensibly nicked! Then, a few weeks on we got picked again. Off to the till, really annoyed - they scan it all and there’s an anomaly between our receipt and their receipt - I asked to see their receipt and there’s an item on there WE DIDN’T BUY. I was livid. It was a four pack of really expensive tinned tomatoes which I’d never buy and obviously, these tomatoes were nowhere to be seen in our shopping… They were at a loss to explain this and were a bit embarrassed when I pointed out that it looked like they were adding stuff to my shop that wasn’t physically there. I also pointed out that if I’d got home and checked the receipt, and then come back to the shop to say ‘I didn’t buy them’, they’d probably be like ‘we can’t know if you did or didnt’, which felt very wrong! Interestingly, our past purchases showed that we might buy something consistently, (example above) then dont, so we could always buy something random (expensive tinned toms) using that logic - it’s funny trying to understand the ‘angle’ that the algorithm is working from! Anyway, next time we went, we got picked again (the algorithm probably had us down as absolute assholes) and after the at we gave up and just went straight to the tills!! I’ll add that this was 6-7 years ago and maybe the system is a bit more elegant now but in the end, it just seemed more trouble than it was worth 😀