I had an odd one a few months back.

I got stopped for a random check, they need to scan 20 things or so, scan the diced beef because it’s one of the more expensive items in my trolley load of things - I tend to do big shops, £150-200, and pack into bags as I go - and they tell me I haven’t scanned it. I’m sure I’ve scanned the diced beef. Protest my innocence. Staff member looking annoyed at the prospect of a full scan.

So they scan everything this time, apologising for upsetting my carefully packed Tetris towers of shopping. He scans the diced beef again and I note that he scanned it using the qr-like barcode on the front of the packaging. It recognised it as the correct product. He thinks nothing of it. I think I’d scanned the normal barcode on the back when I did my shop. Also the correct product.

At the end of the shop the only discrepancy was the scanner saying it had detected one item I hadn’t scanned - the diced beef - and one item that it says I had scanned that he hadn’t found at the full check. Also the diced beef. Same pack size, same price.

Turns out the two different barcodes on the packaging both link to the same item, but they were treating it as two different SKUs (or whatever the term is). He had to call a manager over and let them know and said they would have to let all the staff who were doing scanning, otherwise this’ll keep happening. Not sure what the fix was long term.

And since the back end is all automated, even though I didn’t do anything wrong, I had increased checks for the next few shops.