"a week
after the crash, Boeing distributed a warning to airlines worldwide that a new anti-stall system on the 737 MAX 8 and 737 MAX 9 could cause the aircraft's nose to suddenly drop, resulting in a steep dive. This can occur even when the aircraft is under manual control and when pilots don't expect the flight computer to override their actions.
.."
https://www.extremetech.com/extreme/280521-boeing-737-crash-caused-by-new-safety-system-pilots-werent-told-existed