Continuity check....

Sure, you sound like you are completely isolating the wire run, making a loop, and checking end to end

Your initial description doesn't sound like wire??? You lost me as to where you are losing it.......voltage that is.

Maybe detail "the chain" of the layout.

"Some boxes" have bad troubles where the breakers clip into the buss in the back of the box. When I worked in HVAC, one of the bosses kids had a nearly new double wide home, "all electric." I think it was the dryer started giving trouble. Brand new home, new "cheap" box. Terrible quality.

Years and years ago, "Pacific" (Federal Pacific) something boxes had terrible trouble, and should have all been recalled. Awful stuff. There are still some of those around.

Here's an article on Federal Pacific and Zinsco boxes. The photo illustrates exactly what happened with "the boss's kid."

http://www.ncwhomeinspections.com/arcing+on+zinsco+panels



A breaker used to live here. The quality is poor, the contacts got loose, and arced against the buss