That contact looks like it's been damaged by hot plugging: something's drawing far too much current at the instant the mating contacts touch, and the arc's evaporating the tip of the contact instantly before the rest of the contact has time to heat up enough to melt the plastic. If the current were becoming excessive after the contacts are fully home you would see signs of blueing & discolouration, and possibly molten plastic.
Both my laptop chargers do the same, there's a loud crack as the contacts make, and the pins of the mains plugs are burnt and eroded (along with the corresponding contacs in my sockets no doubt).