During an event titled Autonomy Visualized at a Tesla location in Miami over the weekend, one of the humanoid robots handing out water bottles fell backward after making upward motions toward its head with both hands, according to a video posted to Reddit. (This incident was shortly after Russia debuted its first AI-powered robot, which similarly fell onstage at an event.) The Tesla event was meant to show off its “Autopilot technology and Optimus,” Electrek reported.

It made the movement after accidentally knocking some of the water bottles it was handing out off a desk, and stood out because of its similarity to a human reaction. While it’s unknown what actually occurred during the incident, the robot’s movement led some online to speculate the robot may have been taking off a VR headset. 

Tesla did not immediately respond to Fortune’s request for comment.

Tesla Optimus
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The incident stood out because Tesla has used human-controlled Optimus robots at prior events. During Tesla’s robotaxi event last year, attendees interacted with Optimus robots in person. Some played rock, paper, scissors, while others served drinks or posed for photos.

Yet, it turns out—although the company did not advertise it—some of those bots were apparently being controlled remotely by humans. At least one Optimus robot admitted it, saying: “Today, I’m assisted by a human; I’m not yet fully autonomous,” although the Los Angeles Times reported, at the time, using humans to operate the bots may have been due to a late request by Musk to include the robots in the robotaxi event.

Tesla has previously trained its robots with workers wearing special motion-capture suits and VR headsets.

While Tesla has relied on humans before to showcase their Optimus robots, Musk has often said the robots, in other settings, are not human operated.

In reply to a post on X in October that showed Optimus practicing martial arts, Musk affirmed the robots movements were “AI, not tele-operated.” At the premiere of Tron: Ares that same month, an Optimus robot can also be seen squaring up with actor Jared Leto, a feat that Musk also said was AI-led, not human-controlled.

“Optimus was at the Tron premiere doing kung fu, just up in the open, with Jared Leto. Nobody was controlling it. It was just doing kung fu with Jared Leto at the Tron premier. You can see the videos online,” Musk said during Tesla’s third-quarter earnings call. “The funny thing is, a lot of people walked past it thinking it was just a person.” 

Whether the Optimus robots still rely on human assistance is unclear, yet Musk and Tesla have pinned high hopes on the product, which Musk has called “the biggest product of any kind, ever.”

Musk has projected Optimus could represent up to 80% of the company’s total value, and during the company’s third-quarter earnings call, the CEO said Tesla would next year start  building a production line that could eventually have an annual capacity of 1 million Optimus robots.