In January, my coworker received a peculiar email. The message, which she forwarded to me, was from a handful of corporate Walmart employees calling themselves the “Concerned Home Office Associates.” (Walmart’s headquarters in Bentonville, Arkansas, is often referred to as the Home Office.) While it’s not unusual for journalists to receive anonymous tips, they don’t usually come with their own slickly produced videos.

The employees said they were “past their breaking point” with Everseen, a small artificial intelligence firm based in Cork, Ireland, whose technology Walmart began using in 2017. Walmart uses Everseen in thousands of stores to prevent shoplifting at registers and self-checkout kiosks. But the workers claimed it misidentified innocuous behavior as theft and often failed to stop actual instances of stealing.

They told WIRED they were dismayed that their employer—one of the largest retailers in the world—was relying on AI they believed was flawed. One worker said that the technology was sometimes even referred to internally as “NeverSeen” because of its frequent mistakes. WIRED granted the employees anonymity because they are not authorized to speak to the press.