Side note — If “hidden” bus connections or breaker internals are suspected, and you have a power-rated voltmeter {UL 61010B-1 cat. III or better} “millivolt-drop” tests can be performed on the suspect energized components. See http://ecmweb.com/ar/electric_testing_contact_quality/index.htm Although the gist of the article deals with magnetic starters, the same concepts can be applied to circuit breakers and bus or cable joints.
