Firmware and schematic agree that one output drives the heater and another fires the Deploy 2 pyro charge, but the PCB swaps OUT3 and OUT4. A heater command would energize the pyro output, and neither ERC nor the netlist flags the swap.
From the Grok Haitch pain-radar compilation, finding 218, found 2026-09-14, score 8/10. Low confidence on frequency; severity is the reason for inclusion. Cost model assumes a full schematic-to-PCB pin audit once the class is known.