I started using grocery self-checkouts during COVID, but I’ve kept using them because there’s rarely a line (and I’m a misanthrope). I’d probably go back to using regular human checkouts if I had to dig through all my crap to prove what I bought.
Having said that, I’ve noticed myself making mistakes. I’ve accidentally failed to scan an item, and I’ve accidentally entered incorrect codes for produce. When I notice, I fix them, but I’ve probably missed a few.
I guess the easiest answer is for grocery chains to reinvest some of those windfall profits and hire more cashiers.
Costco also has actual cashiers working, and an extra person to bag your groceries on top of that typically. And they pay better than the typical grocery store.