The conclusion that two of the AoA sensors failed, comes from the fact that the values "do not make sense" at some point in time; and also from the fact that the values are not changing. Of course I don't know, but I presume neither of these clues is taken into account by the system to (in)validate the data? The two wrong AoA values do seem to agree with each other, though. Would the third (supposedly good) data be discarded in such a situation, without any sort of warning?