UPDATE 5-U.S. regulator cites new flaw on grounded Boeing 737 MAX

WASHINGTON/SEATTLE, June 26 (Reuters) - The U.S. Federal Aviation Administration has identified a new risk that Boeing Co must address on its 737 MAX before the grounded jet can return to service, the agency said on Wednesday.The risk was discovered during a simulator test last week and it is not yet clear if the issue can be addressed with a software upgrade or will require a more complex hardware fix, sources with knowledge of the matter told Reuters.The FAA did not elaborate on the latest set