Hitting its goal of making 20,000 Optimus robots per week is reportedly proving tricky for Tesla. The Information reports that Tesla produced “several hundred robots a week” last month, after it repurposed its Model S and Model X production lines for Optimus earlier this year. However, this strategy is reportedly creating manufacturing snags, like issues lining up parts precisely, as The Information notes: “Not only are the Optimus production lines new, but the Optimus parts are much smaller and have to fit together far more precisely than car parts.”

It reports that even in the “V3” Optimus robots it’s currently producing, the hands and forearms “have more than 100 screws and other small components that currently require a worker to assemble manually.” These robots are lighter and have more cameras than previous versions, but lack a “sensing glove” currently in development that will improve durability by making it easier to replace touch sensors without swapping out the entire hand.

Optimus has faced delays for years now, even as Tesla CEO Elon Musk has made bold promises about it, saying Optimus will be Tesla’s “biggest product of all time.” However, at the moment they’re still being used internally for specific tasks in limited areas, and not generally or with remote teleoperation. Tesla also reportedly plans to lease the robots initially rather than selling them, and use the training data collected to improve the robots, but it will have to get them out in the world first.