Uber’s human drivers have started ratting on their robot colleagues in Pittsburgh.

Driver Nathan Stachelek told Quartz that he was parked on the side of the road during a shift for the ride-hailing service on Sept. 26 when he saw one of the company’s self-driving car prototypes start heading the wrong way down a one-way street near the University of Pittsburgh.

Stachelek said it was too far away to tell if the car’s computer was in control when it made the wrong turn, but he posted a video on his Facebook page that shows the back-up human driver that’s required to be on board at all times turning the car around and getting it headed in the right direction.

There did not appear to be any passengers in the car at the time.

Two days earlier, on Sept. 24, another Uber driver came across one of the self-driving cars – easily identifiable by a large collection of sensors on the roof – parked on the side of the road in front of another vehicle with its hazard lights flashing. A man wearing a lanyard was inspecting the cars, suggesting there had been a minor collision. Uber confirmed to Quartz that there had been a “low-level” incident reported that evening, but said it didn’t know anything about one of its cars turning down a one-way street.

A Pittsburgh police spokeswoman told Quartz that the department was unaware of any accidents or incidents involving the cars, and that it does not have any kind of information sharing agreement with Uber. So, unless an event occurs requires a police response, there’s no way the police would know about it.

Uber is currently operating a handful of self-driving Ford Fusion Hybrids that are accessible to a select group of its customers, but plans to expand the semi-autonomous fleet with 100 Volvos in the next few months. The cars can only operate within the city limits, and the company says that it expects they will often require their human drivers to intervene as the technology is developed.