How could Wyrick have known it was intermittent? What I mean is, had it been on when he passed her, he then slowed and stopped her for no good reason, but then the investigation showed that they had been having intermittent problems with the headlight, I'd say that was the most amazing stroke of luck that Wyrick will ever have in his life. That's borderline "divine intervention."

Accept the obvious - he stopped her because the headlight was out at the time he passed her. To assume otherwise is pure folly.