On Thursday, January 21, 2016 at 3:00:24 PM UTC-5, E. Robinson wrote:
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.

Great!

And thanks for getting back to the group.

One common scenario he the OP writes in with a problem, the group discusses back and forth, the OP disappears, the thread dies, the thread is resurrected 10 years later, the argument continues.

Just a comment: the sooner you are sure what is wrong, the more you find it impossible to see contrary evidence. Troubleshooting is best with an open mind. And don't forget there can be a bad breaker AND a short.

I looked up breaker longevity some time ago and don't remember the exact numbers, but they were in this neighborhood. A breaker can be turned on and off something like 30,000 times before it wears out. It can trip on mild overload maybe 1-3000 times. But a dead short drawing full available current will kill it in 1 to 2 times.