Metro workers test new 7000-series cars at the Shady Grove station in 2014. (Bill O’Leary/The Washington Post)

Metro will need to rewire all of its 7000-series rail cars over the next year after internal inspections discovered wire crimping defects that were not found during manufacturing, according to the agency.

The new quality-control report concludes that Metro will need to rotate each of the 548 cars out of service over a year or more to address the problem. The review said manufacturer Kawasaki failed to discover the defect during manufacturing, and the problems were found by Metro crews during inspections at the manufacturer’s Lincoln, Neb., plant. Metro says the issue could affect the railcars’ long-term reliability.

“The manufacturer for the 7000-series rail cars has failed to implement an effective system for conducting in-process inspections,” the report says.

The review says that Metro should order stricter quality-control practices from manufacturers by strengthening its contract language.

Metro halted delivery of the 7000-series cars upon discovering the issue, but plans to resume the process later in August, the agency said, adding that it will not be charged for the maintenance work to address the wiring issue.

Metro is investing $2 billion and substantial resources in the 7000-series, the agency’s next-generation rail car that replaces the 1000-, 4000- and 5000-series cars. The cars are expected to constitute 748 of Metro’s 1,200 rail cars when the delivery is completed by July 2019. By last month, Metro says it had received 564 rail cars — 548 of which had been put into service.

But the findings raise new questions about the quality and durability of the rail cars, despite the fact that they have become Metro’s best-performing fleet, according to the agency’s rail reliability statistics. This summer, the Federal Transit Administration ordered Metro to install chain barriers on all of the 7000-series cars because of a safety issue where passengers with visual impairments could fall through the gap between trains. FTA, which is responsible for Metro safety oversight, said the existing rubber barriers were insufficient and ordered a fix by Dec. 31.

Metro has said Kawasaki cannot meet that deadline because of a supply issue but says the work will be completed by May.

The FTA said Tuesday it is monitoring Metro’s response to the wiring issue and that it has no information to suggest the defects pose a safety risk.

Metro noted in its quality-control review that Kawasaki has significantly reduced the number of defects on new car arrivals, from an average of 22 per car in May 2016 to six in May 2018. The agency said it is using an eight-car maintenance facility in the region to support repairs and modifications for the cars.