Seen the Chargers do this lots, way too often.
I've always associated the Chargers with lousy defenses. I suspect that it goes back to the days of Dan Fouts. Remember that playoff game in the early 80's when SD was up big against Miami in the first half but had to go into OT to win? Fouts probably would have a Super Bowl ring or two if he hadn't played for a team where he had to score a touchdown on every offensive series.