Simply stated, Boeing rushed the ac into production to counter the NEO series. The extended landing gear to counter the long standing issue withe engine size, larger diameter engines that weigh far more, yet no new wing design.
Put them further forward and higher on the wing to fit, and when instability issues show up, a software patch. Forget to mention this in the FCOM or training.
It appears to get the ac to actually fly, you have to turn off the AP....
Broken dreams or broken promises?