I know one of the people who worked alongside Klein (and Unidan) at Binghamton U. She says wild crows are highly neophobic and it's hard to train them to accept the presence of a big machine and do stuff with it. (Our conversation was quite a few years ago so I'm a bit vague.) There was a lot of academic disagreement and fallout when Klein went forward with his Ted talk and made the experiment out to be much more exciting than it was.
There was a similar project — under the delightful name “Crowbar” — to train crows to gather cigarette butts. Ran out of funding. https://www.crowdedcities.com
Yeah, I've seen multiple instances of people claiming to have done this, but they always turn out to be scams. I believe a crow could he easily trained to move a bottle cap already on a table to the reward mechanism, but so far no one has ever shown birds coming with wild caught bottle caps to get more food.
Although I seem to remember reading that the vending machine never worked as well as the inventor said.