Curious. Obviously this is just just anecdote, but all the shops I use regularly (in the UK) have been increasing the number of self-checkouts and upgrading the systems. My local Waitrose has stripped out a whole load of basket tills and replaced them with a larger self-checkout area with upgraded hardware that is noticably better/more reliable. Perhaps this is a location or shop specific effect?
One where you use a remote to scan the products as you add them to cart, then just put away the remote. The other one where you scan at the station.
I would say I see 5x reduction of actual people working behind the checkout.
And I basically rarely wait in queues any longer.
I have never witnessed a singular tech failure either.