It's not a software issue because the software was working excatly as specified. There is no bug. And its not really an aerodynamic issue either. Boeing have

It's not a software issue because the software was working excatly as specified. There is no bug. And its not really an aerodynamic issue either. Boeing have a massive procedural issue where they didn't do proper safety analysis of how the system works as a whole. The fact that they didn't identify this failure case as a major issue makes you wonder what other failure cases (on other planes too) that they missed. The original version of MCAS only moved the stablizer by 0.6 degrees, and only in situations with high angles of attack AND abnormally high g loading. That's the version they ran the safety analysis on, it relies on two types of sensors that shouldn't fail simultaneously. Later they modified MCAS to move the stablizer by much larger amounts (2.6 degrees, 4x larger) and they removed the high g loading restriction so it would operate in more situations. This also means it was now relying on a second sensor. And they never re-ran the safety analysis.