When I was working as an electrician ,when we rewired homes we were required to repair / replace any wiring that was obviously hazardous , illegal or unsafe. This led to a lot of problems
Many times it meant tearing out the wiring done by the homeowner and reinstalling it properly . The further you dug into the wiring the more you found things that were wrong.. I once filled a 2 yard dumpster with homeowner wiring I had to rip out. This led to arguments over the bill and on several occasions ended up in court.
If I was an electrical
contractor , I would avoid working on your trailer because there is no way to estimate the cost or how much of the wiring needs to be replaced. In many instances , it is cheaper to rip it all out and start from scratch. A licensed contractor does not want to stick his neck out and face future liabilities.
We often got calls where people did their own wiring and wanted us to hook it up in the panel and certify that the wiring was safe and to code. We would refuse to comply with their request .