every trailer company has Stevie wonder install the wiring .
We have bought brand new trailers and had to replace the wiring and or connectors
it’s usually the connectors , I prefer wire nuts wrapped with electric tape to the poor quality crimp connectors the trailer manufacturers always use .
If you wanna go high quality , get the wire nuts with the epoxy goo inside .
and if you can find a replacement backing plate that’s loaded with everything , just get it and bolt it on and be done .