On Thu, 21 Jan 2016 08:07:38 -0500, Stormin Mormon wrote:

You did get some really good answers, including to just
pull the breaker out and replace it, they often aren't
that expensive. Also swap two black wires, and see if the
problem follows the wire or the breaker.

The best answer was to shut the mains off, and then test
the circuit breaker. That is a great test, and it showed
the problem.