The assumption that this was a failure of a water heater trip switch again brings into light the question of quality management/control. In the (unrelated) battery farrago there was much speculation about the quality of the parts. It would appear that a circuit breaker may have been to blame here, not necessarily performing as advertised. Sure, it may just have been one of those duff, Friday afternoon parts but Boeing can ill-afford to have such events right now.
If I was one of those Boeing Board members who are probably sat around the conference table this weekend, I know what I would be concentrating on.