Fog yes, but one of the three redundant guidance units malfunctioning? No. In fact, pretty much any hardware problem or malfunction will prohibit CatIIIb landing, which is common in current aviation. Craft will regularly fly with "minor" hardware or sensors in an inop status.
Basically to let the plane land itself, first the stars have to align
Basically to let the plane land itself, first the stars have to align