Im fascinated by flight and aviation so to explain the issue here, the suspicion is falling upon the MCAS system which is software new to the MAX 8 that automatically pitches the nose down if it senses an abnormal angle of attack reading. This is possible because the engines on the MAX 8 are larger and farther forward than previous 737's and can cause the plane to nose up immediately following take off. The MCAS is meant to eliminate this.
The LionAir crash report isnt finalized but the belief is there was a faulty angle of attack sensor which caused the MCAS to nose down the plane (put it into a dive) and this confused the pilots were didnt know why it was happening or how to stop it.
Disengaging the MCAS is apparently easy to do but what is coming out now is that pilots were not sufficiently trained on it. The FAA considered the MAX 8 to be similar enough to the 737NG that it did not require simulator training. Pilots have complained they have not been fully trained. Also, previous auto-pilot issues can be disengaged with manual pressure applied to the control column but that does NOT disengage MCAS. So a pilot experiencing a sudden nose down would instinctively pull back...and nothing would happen.
The Lion Air pilots only received 3 hours of online training.
As we see above, several pilots have filed reports indicating control issues with the MAX 8. I think its clear that there is an issue with the plane even if its just a matter of insufficient training. I read one account where pilots basically fought the MCAS, trimming nose up as the system tried to nose down, creating a roller coaster flight.
I saw that Air Canada's flight attendant union wants the planes grounded or for Air Canada to let employees switch off the plane if they arent comfortable.