Loss of 12v power when shore power is disconnected

The high voltage was a bad meter and that has been resolved. I cut into the corrugated plastic under the 5th wheel to trace my wire. When I did acorn shells were found, I may have a rodent issue. We will see tomorrow. What I do know is where the wire leaves the circuit breaker and disappears I have power and where it re-emerges at the rear of the panel I don’t. Tomorrow I will fine the cause.