Tesla began producing electric cars at its plant in Fremont, Calif., six years ago, starting with small quantities and ramping up to about 100,000 vehicles last year. Now, as it tries to double or triple that number, the company and its chief executive, Elon Musk, are getting a lesson in how hard it is to mass-produce automobiles.

On Tuesday, Tesla reported that it had managed to increase production of a crucial new model in the first quarter of 2018, although it remained well short of the company’s already lowered target. At the same time, it encountered a new hitch — a drop in sales of its two established products, the Model S sedan and Model X sport-utility vehicle.

The company is counting on the success of the new offering, the Model 3, to increase revenue and help pare its losses as Tesla invests heavily in the vehicles it hopes to offer in the future.

But a series of setbacks have left Tesla far behind schedule in turning out the Model 3 — for which nearly 400,000 prospective buyers have already put down $1,000 deposits — and it is taking some extraordinary measures to turn things around. Mr. Musk said on Twitter this week that he had been sleeping at the plant, and the company said some workers who normally assemble the Model S and Model X were shifted to Model 3 production.