I've seen plenty of lug bolts like that working in the factories. If you look at the wire above the glowing nut you will see it's been rewrapped as the insulation has burnt off before so this is an ongoing issue.ALL of the other nuts/bolts/washers look brand-spanking new. is this an on-going issue? there should be no way that the nut is the hottest part when no power is actually flowing through it headed elsewhere. that's a dead end that should only have radiated heat affecting it. that wire/harness does show a "little" history compared to its neighbor.
needs a longer leash. "to boldly go where no dog has gone before, and pee on the upper branches"