In order to deliver all those next-day deliveries on time, Amazon uses millions of subcontracted drivers for its Flex delivery programme, started in 2015. Drivers sign up via a smartphone app where they can choose shifts, coordinate deliveries and report problems. Think of Uber’s false sense of freedom for its employees and you’ve pretty much got the same thing happening here with Amazon Flex. But the reliance on technology doesn’t end there as drivers are also monitored for performance and fired by algorithms with little human intervention, according to a recent Bloomberg report.

As much as we love and depend on algorithms, it’s crucial that we understand how even those can mess up from time to time. According to the report, the AI system used by Amazon Flex can often fire workers seemingly without good cause. One worker said her rating—ranging from Fantastic, Great, Fair, or At Risk—fell after she was forced to halt deliveries due to a nail in her tire.

Over the next several weeks, she managed to boost it to Great but her account was eventually terminated for violating Amazon’s terms of service. She contested the firing, but the company wouldn’t reinstate her.

Another driver was unable to deliver packages to an apartment complex because its gate was closed and the residents wouldn’t answer their phones. Shortly after, in another building, an Amazon locker failed to open. His rating quickly dropped and he spent six weeks trying to raise it, only to be fired for falling below a prescribed level.

In those instances, when a driver feels they’re wrongly terminated, there’s not much recourse, either. Drivers must pay $200 to dispute any termination, and many have said it’s simply not worth the effort. “Whenever there’s an issue, there’s no support,” said Cope, 29. “It’s you against the machine, so you don’t even try.”

Amazon became the world’s largest online retailer in part by outsourcing its many different operations to algorithms. For years, the company has used algorithms to manage the millions of third-party merchants on its online marketplace, drawing complaints that sellers have been booted off after being falsely accused of selling counterfeit goods and jacking up prices.

More and more, the company is also ceding its human-resources operation to machines, using software not only to manage workers in its warehouses but to oversee contract drivers, independent delivery companies and even the performance of its office workers. People familiar with the strategy say Jeff Bezos believes machines make decisions more quickly and accurately than people, reducing costs and giving Amazon a competitive advantage.

Inside Amazon, the programme has been praised for its success. Around 4 million drivers have downloaded the app worldwide including 2.9 million in the US, according to Bloomberg’s report. More than 660,000 people in the US have downloaded the app in the last five months alone.

Amazon said drivers’ claims of poor treatment and unfair termination were anecdotal and don’t represent the experience of the vast majority of Flex drivers. “We have invested heavily in technology and resources to provide drivers visibility into their standing and eligibility to continue delivering, and investigate all driver appeals,” Spokesperson Kate Kudrna told Bloomberg.