Right, I think the video explains it. In short, and what I've read elsewhere: The jet engines were not designed for this plane, but they used it anyway, maybe to save some money. So it doesn't really fly stable without software correction, because they are mounted at the wrong position. The software depends on sensor inputs, and I've read these AOA sensors are not redundant and can fail. If this happens, the pilot has to understand that this is the problem, and then do 3 non-obvious steps to counteract that the nose dips and that it falls out of the sky.