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Widerĝe pilots are well trained and experienced.
I doubt that they were stalled, windshear yes, certainly possible in between high mountains.
You can easily get a windshear-stall in bad windshear. Not so common in faster aircraft, but well known in gliding, where it is known as the 'clutching hand'.
Mind you I have seen a few raw jet f/os wondering why the aircraft plonked down so hard, when everything looked fine. - They did not see the impending low-level windshear that can reduce lift even in a jet. Not quite a stall, but certainly enough to drop you a hundred meters or so.
S