Elon Musk tweeted a video of the Tesla Model 3 assembly line on Sunday. The video shows automated robots inside Tesla's Fremont factory working on the bare-metal body of a Model 3, the electric-car maker's first mass-market vehicle, which began shipping in the third quarter of this year.

Tesla last week showed that it produced just 260 Model 3s during that period, falling far short of its goal to crank out 1,500 of the cars in September. Tesla blamed the shortfall on "production bottlenecks."

Watch the Model 3 assembly line video below:

The Model 3 body line slowed down to 1/10th speed A post shared by Elon Musk (@elonmusk) on Oct 8, 2017 at 3:20pm PDT Oct 8, 2017 at 3:20pm PDT

"Although the vast majority of manufacturing subsystems at both our California car plant and our Nevada Gigafactory are able to operate at a high rate, a handful have taken longer to activate than expected," the company said in a statement on Monday. The shortfall has also cast doubt on Tesla's ability to produce the 20,000 Model 3s per month that it said it would reach by December.

The video from Musk also comes two days after The Wall Street Journal reported that slow Model 3 assembly line progress was due in part to factory workers having to make some of the car's parts by hand; ostensibly because factory equipment was not yet ready for use.

A Tesla spokesperson refuted that claim in a Friday night email to Business Insider: "We are still in the beginning of our production ramp, but every Model 3 is being built on the Model 3 production line, which is fully installed, powered on, producing vehicles, and increasing in automation every day," the spokesperson said.

News of the Model 3 production challenges likely won't rattle Tesla investors or its customers, Business Insider's Matt DeBord noted on Saturday, adding that Tesla stock is still up 65% in 2017 and the brand has lost none of its captivating aura. And the video perhaps proves that despite the hiccups, Tesla has lost none of its mojo, either.