I always notice people are super cocky about this kind of thing. Yet self-checkouts are so fucking terrible it basically everyone runs into problems at them eventually. So just tempting fate from everyone in this thread really.
I don’t know how you can go wrong. You scan the thing, set it down, repeat. Press pay, scan your card, done.

Unless you get booze, need to use cash, or it’s an item the machine wants to weigh. Or worse, expects the weight to be different than it is.

At least most places seem to have turned off the weight thing off (or it got ‘smart’ enough to not care so much).