As someone who uses self-checkout machines effectively, this happening is fine. I have a moment of confusion, then find the code, then move on to the next item.

As someone who uses self-checkout machines effectively, this happening is fine. I have a moment of confusion, then find the code, then move on to the next item. What is terrible is when instead of the self-checkout machine throwing a warning about it not being scanned correctly, so I can find and input the code, it just locks up the machine and says "Customer needs assistance". Then I'm in the same boat as the clueless folks, because the machine won't trust me to correct.