I'm tentatively putting my $10 on a failed jack screw.
I think
that lesson has been learned by everyone in the aviation industry. These are the accidents that only happen once, and then make it into all textbooks. (on the other hand it has been the nut, not the screw, so maybe you just give an example that not everybody has learned the lesson correctly...)
German news were reporting about heavy sandstorms in the area, how high can they possibly reach?