The authority has hired an outside firm to inspect the faulty cars and has replaced them for now with others in its roughly 6,700-car fleet. The move has resulted in trains running less frequently on the J and Z lines, officials said. It was unclear how long the inspections would take.

“There is nothing more terrifying than the idea of a door flying open when you’re leaning against it,” said Nick Sifuentes, the executive director of Tri-State Transportation Campaign, an advocacy group. “But from a safety perspective, it’s good that this is being flagged now and can be rectified immediately.”

A Bombardier spokeswoman said on Wednesday that the company’s own investigation of the cars, which prompted the authority’s action, showed that the doors had not been properly calibrated by a supplier, Nanjing Kangni Mechanical & Electrical of China.

She declined to elaborate.

“We are now inspecting all of the R-179 cars and, where necessary, making adjustments to ensure the safe and reliable performance of the doors for the entire fleet,” she said.

Modernizing the subway-car fleet has been a priority since the system fell into crisis in 2017 and Gov. Andrew M. Cuomo, who controls the authority, declared a state of emergency.

The M.T.A.’s contract with Bombardier has been troubled with delays and design flaws since the first R-179s were delivered in 2016. Several cars were pulled from service last January because of software defects.

The extent of the problems was outlined in an audit by Scott M. Stringer, the city comptroller, in December. The audit faulted Bombardier for performance issues and found that the authority had not sufficiently held the company accountable.