Amazon-owned self-driving car company ZOOX released its second voluntary software recall within a month after a collision between a robot and an E-type driver in San Francisco on May 8.

The latest incident involved a vacant ZOOX vehicle running at low speeds, and the company said it suffered a hit from an electronic cab at the intersection after braking.

Just a few weeks ago, the company recalled Las Vegas' crash between Zoox Robotaxi and a passenger car, which raised concerns about the ability of autonomous driving software to predict movement of other road users.

This question still seems to be a problem.

"The Zoox vehicle was stopped at the time of contact," the company wrote in a statement on the May 8 crash. "The electronic dancer fell on the ground next to the vehicle. The robot then began to move and stopped after completing the turn, but did not have further contact with the electronic protesters."

According to Zoox, the electronic driver turned down medical services for minor injuries.

Zoox said it shares relevant information and videos with regulators and has released software updates to “improve perceptual tracking and further prevent vulnerable road users from acting when they are near vehicles.”

Robots that continue to move after a collision may harm other road users in the crash. Just look at what happened to Cruise, the former competitor of Zoox. The GM-backed company saw one of a robot whose business collapsed, hitting a pedestrian who was hit by a human-driven vehicle and then dragging about 20 feet of pedestrians while trying to do a pullover.

TechCrunch has reached out to see if this is the biggest concern when ZOOX issues a software recall, or if there are other factors at play, such as unexpected hard braking.

In March, Zoox recalled 258 cars because problems with its autonomous driving system could cause unexpected hard braking, after two incidents reported that motorcycle riders collided on the back of the Zoox test car.

ZOOX did not respond to TechCrunch in a timely manner, unable to confirm more details about its latest software recall, including the affected vehicles, and how this update differs from the update released a few weeks ago.

TechCrunch has contacted the National Highway Traffic Safety Administration for more information on the recall.