An agent-driven router placed a GND plane-tap via dead centre in the USB plug's GND contact finger: the mating surface that slides into the socket. A drilled hole there damages the plating the socket wipes against, and nothing graded it: check_drc sees a same-net via in a same-net pad as legal copper, check_assembly said buildable, and board_score reached blocking 0, so the defect shipped with every grader clean.