Tesla's slower-than-expected Model 3 production rate has fanned worries about Tesla's cash flow and capital expenditures — major ongoing concerns for investors.

Analysts have again expressed concern over whether Tesla can secure the gross margins on the cars it is aiming for, whether customers will still want the car, and how slower production rates affect the company's other capital-intensive ambitions. These include the construction of new factories, the buildup of the solar and battery business, and the introduction of new models, such as the Tesla Semi, Roadster and Model Y.

Tesla announced delivery and production numbers for the fourth quarter of 2017 on Wednesday.

Tesla shares were down 3 percent Thursday morning.

The successful launch of the Model 3 is crucial to stemming Tesla's cash burn, which hit a record $1.4 billion in the third quarter, said J.P. Morgan analyst Ryan Brinkman in a note sent Thursday.

But it was already difficult to see how Tesla can sell the Model 3 at its $35,000 starting price and pull in 25 percent gross margins, which are typical of higher-end luxury cars, Brinkman said.

Tesla had said the Model 3 was designed for quicker production than the more complicated Model X.

But the company has so far has pushed back its target of making 5,000 Model 3's per week twice. The slowdown may mean the car is tougher and more expensive to manufacture than the company had thought, Brinkman said.

"Perhaps the issues that have significantly hobbled the Model 3 ramp really can be fixed in a cost-effective manner and shortly cycled past (although this did not happen in 4Q)," Brinkman said. "But we rather suspect that the materially missed launch cadence could be the result of too optimistic assumptions on the company's part as regards the ease of manufacturing the Model 3."

Slow production could affect the number of Model 3 buyers who receive the $7,500 federal electric vehicle tax credit, and it is unclear whether this may drive away buyers, said Cowen analyst Jeffrey Osborne.

In addition, Tesla's other capital-intensive plans, such as factory construction, may have to be pushed back to 2019 on account of the slower production ramp, he said.

Others are more confident. Baird analyst Ben Kallo said in a note Thursday he thinks the company's ability to expand gross margins will improve over the next three to four quarters.