The problem was discovered during a technical check.

Boeing has discovered a new vulnerability in the software for 737 MAX Airliners. Reuters reported this on Friday.

According to it, the problem was discovered during a technical check before the development of the updated software was completed. What exactly the vulnerability is not yet reported.
The company informed that it is in contact with the Federal aviation administration (FAA) of the United States on this issue.

Operation of the Boeing 737 MAX was suspended after two disasters. On March 10, 2019, an Ethiopian Airlines Boeing 737 MAX 8 crashed in Ethiopia, killing 157 people. On October 29, 2018, 189 people were killed in the crash of a similar Lion Air model.

Boeing management acknowledged that in both cases, there was a failure in the maneuverability improvement system on Board the aircraft before they crashed. After that, many countries, including Russia, the United States, and the European Union, suspended the operation of this series of aircraft for security reasons.