Metro found some door components on 4000-series railcars to be at a "low level of acceptable tolerance" with Metro standards after an inspection over the weekend, according to a Metro release.
Metro will gradually return the 4000-series cars into service as maintenance work is completed over the next month, Metro said. It was previously expected that all trains would be back on the tracks this week.
Meanwhile, there will be more six-car trains than eight-car trains on the Red, Blue, Orange and Green lines.
Metro inspected the 100 4000-series cars pulled from the rails over the weekend after a video captured by riders showed a train door wide open while the train was moving.
The inspections revealed no evidence of a systemic or emergency safety hazard, although some of the Metro door components were barely keeping with Metro standards, Metro said.
The maintenance includes adjusting tension on doors, switches, checking all screw mechanisms, and doing further inspection. The suggested adjustments will require more time to fix than just overnight hours, Metro said.
Eventually the 4000-series trains will be phased out by the newer 7000-series trains, which launched June 8.