These things are always multi-factorial... You can blame the mechanics for not fixing the problem.... You can blame the pilots for not following the right procedure.... But really there is only one party here to blame. And that is Boeing.....
They designed a crazy system, as if the AoA sensor is god and the pilot is stupid.... So no matter what the pilot does (apart from turning the damn thing off), the system will repeatedly drive you into the sea.....
Yes you can blame the mechanics. Yes you can blame the pilots. But at the end if the day, it is Boeing that thinks the AoA sensor has more authority than the pilot......... And that, in my book, is pretty bloody stupid......