Tesla chief Elon Musk claimed in January that he believes its Optimus humanoid robot business will be worth “north of $10 trillion in revenue,” but a recent video suggests there’s still plenty of work to do on the contraption.

In an embarrassing turn of events last weekend, Optimus lost its balance and crashed to the ground during a special gathering called “Autonomy Visualized” held at a Tesla store in Miami.

As the video (below) shows, the robot appears to grab at a bottle of water on a table, but somehow manages to knock over all of the bottles around it. It then falls backwards, hitting the floor.

But as noted by numerous commenters online, the most interesting part of the clip is how the robot’s arms move up toward its head just as it loses control, suggesting that the robot was being teleoperated at the time, instead of acting autonomously. In other words, Optimus was replicating the moves of a Tesla engineer, who then pulled up his or her VR headset just as the robot started to fall.

Teleoperation is still commonly used among those developing humanoid robots, though Tesla has never explicitly stated that Optimus is controlled via such a method. 1X Technologies recently opened preorders for its home-based robot helper called NEO, but admitted that during the trial stage, more complex tasks will be handled using remote teloperation while they continue to build out its autonomous AI-powered smarts.

Now, Tesla has yet to say what exactly caused the fail, but the mishap with the water bottles and then the “fainting” episode appear to suggest that it still has some way to go before it can realistically fulfill its promise to equip its auto plants with the robot, carrying out various tasks alongside human workers.

Musk is expecting Optimus to eventually generate more revenue that Tesla’s auto business, but witnessing the Miami debacle after four years of development will leave many wondering if it’ll ever happen.

That’s because building a truly autonomous humanoid robot has turned into a multi-billion-dollar race involving a growing number of tech companies around the world. The first player to produce that robot could end up dominating the market, and with companies like Unitree already turning out some impressive-looking robots like the G1 and H1, Tesla looks to be some way behind. But it has to be said, even Unitree has much work to do before it can claim to have created a truly versatile, autonomous humanoid robot capable of competently performing a range of tasks, so everything’s still to play for in the rapidly evolving sector.