electric issue....outlets not working

[targell]

I have a 2004 DRV and have half the outlets on a run not working. replaced circuit breaker, had an electrician check it out. He said I had power to the main outlet that fed the rest not working but not enough to make anything work He said I had a black wire and copper wire touching some where. he pulled all the outlet down the run from the last one working. everything is fine. he said "it has to be in the wire coming from the ceiling". By the way ....the outlets not working are in the biggest slide out and end of fifth wheel. he kept saying "You have a pinched wire ...like the black wire and copper are touching somewhere." I have no idea where to look. so question is how does the line come from the breaker? we know it goes to bedroom and everything works there but it also feeds the front left side and front end to include the slide out. Can there be two wires off a breaker going both direction? how does the wiring get to the end of trailer thru the ceiling or under carriage? an electrical diagram would help a lot. Tks