Tesla shares have dropped more than 20 percent from an intraday all-time high set roughly two months ago in mid-September.

The Tesla Semi and second-generation Tesla Roadster created a buzz since they were unveiled on Thursday. But some investors remain concerned over issues such as whether Tesla can deliver on both its production goals for the Model 3, and secure the gross margins on the car that management expects.

Tesla hit an intraday all-time high of $389.61 on Sept. 18. Since then the stock has fallen more than 21 percent. The shares began drifting downward in late September, and took a big step down around the time the company reported third-quarter earnings. Those results missed expectations by a wide margin.

On Monday, Tesla’s stock was down more than 2 percent, at around $308.

Tesla’s management recently expressed confidence that gross margins on the Model 3 would be 25 percent, said JP Morgan analyst Ryan Brinkman in a research note sent Monday. But competing automakers with greater purchasing power and the ability to amortize fixed costs across a greater number of units, do not achieve 25 percent margins on similarly priced vehicles, Brinkman said.

Competitors also do not price their own electric models to be profitable, but instead to offset the sale of internal combustion engines in states with emissions regulations. Finally, electric powertrains are still more expensive to make than internal combustion engines, Brinkman said.

“Driving the Model 3 was exciting and we expect the car will prove popular with consumers, but while management expressed confidence in achieving (recently delayed) production targets and attaining a (reiterated) 25% gross margin, we still see challenges,” he said.