Amazon-owned Zoox says it issued a software recall for all 270 of its vehicles after an unoccupied robotaxi in Las Vegas crashed into a passenger vehicle on April 8th, Reuters reports. The update rolled out between April 16th and 17th to address a risky situation that could arise when the vehicle operating at over 40mph closed in on another vehicle that approaches its lane from a perpendicular driveway before stopping.

In a press release on Tuesday, Zoox said there was only minor damage to both vehicles and no injuries were reported. Zoox shared how the incident played out in the voluntary safety recall report it sent to the National Highway Traffic Safety Administration (NHTSA) on May 1st:

The incident involved a passenger car quickly approaching the lane where our purpose-built robotaxi was traveling. Anticipating that the passenger car would proceed forward, the Zoox robotaxi slowed down and steered to the right. Instead, the car came to a stop, fully yielding to the Zoox robotaxi and remaining in the shoulder lane. The Zoox robotaxi braked hard, but contact was unavoidable.

The report states that, prior to the update, the company says, “In situations where Zoox vehicles are operating at speeds greater than 40mph, and a vehicle incrementally encroaches from a perpendicular driveway approaching the Zoox vehicle’s lane, the Zoox vehicle may make an inaccurately confident prediction that the vehicle is going to proceed into the Zoox vehicle’s lane.” Reacting based on that inaccurate projection could cause a crash, as happened here.

A March recall notice from Zoox also notes that after two incidents where its Toyota Highlander-based robotaxis performed sudden hard braking, causing approaching motorcyclists to rear-end them, it rolled out a software update to address the problem last November.