It looks like a loose connection on the shore power neutral. A loose causes excessive heat that causes more damage to the other conductors. The neutral busses are normally aluminum and very seldom copper. The aluminum oxidizes which can cause the connections to loosen.
I am a strong advocate for servicing the connections in the power center. This entails disconnecting the conductors, cleaning them, applying good coating of electrical grease and then re-attaching them.
Look for some kind of access to the conductors behind the panel to see if there is any slack. If there is, pull sufficient amount to re-terminate the wires.
