(CNN) Boeing's troubled 737 Max has run into a new glitch.
During a recent technical review involving the Max, Boeing observed an issue with the plane's flight computers, according to a source familiar with the matter.
The source said the issue is not related to the software revisions Boeing made to address the cause of two fatal crashes that killed 346 people, and would not occur during flight. The Max has been grounded since March following the second of those crashes.
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The computer issue was observed when booting up the computers on a Max and involves the so-called software power up monitoring function, which checks for anomalies when turning on the computers. It's similar to the steps any computer might make when first turned on. The source said the process of turning on the computers is performed when the plane is on the ground, rather than in flight.