Tesla is now building several hundred Optimus humanoid robots a week, up from just a few dozen in the second quarter, according to a report in The Information. Managers want to reach 1,000 a week by the end of 2026.

The ramp is being held back by the robots' hands. Each hand and forearm contains more than 100 tiny parts and screws that workers must still assemble by hand, and touch sensors in the fingers have been unreliable, the report said. Tesla is developing a replaceable sensor 'glove' to make repairs easier.

Suppliers, many in China, also struggle to keep up quality as volumes rise, and the robot still takes several days to learn basic tasks. Tesla plans to lease early units to partner companies to gather real-world training data.

Tesla has converted former Model S and X production space in Fremont to build the robots, with a longer-term ambition of 20,000 units a week.

Despite the problems, CEO Elon Musk still calls Optimus Tesla's future biggest product.