They recommended to 16 customers that they address a potential electrical issue in a specific group of 737 MAX airplanes prior to further operations

Boeing managed to get the 737 MAX back into the late last year after it was grounded for 20 months following two fatal crashes

Boeing reveals 'potential' 737 MAX issue

A Boeing 737 MAX 7 aircraft lands during an evaluation flight at Boeing Field in Seattle, Washington, U.S. September 30, 2020.