More pictures needed. Which wires come out of the chassis? Which wires go into the brake drum? Which wires are connected to grounding points?
Lots of electrical connector solutions. Go with something marine grade such as:
Solder butt connectors & a heat gun: https://www.amazon.com/Kuject-Connec.../dp/B073RMRCC3
Here's how they look in use: https://www.jaycoowners.com/forums/f...tml#post854281
Or put marine grade adhesive shrink tube over top of standard crimp-style butt connectors: https://www.amazon.com/Ginsco-270Pcs.../dp/B073R69KNB
Check YouTube for lots of videos on splicing wires and/or using those soldering butt connectors.
I had tons of corrosion underneath the wire insulation on my brake wires because Jayco used such shoddy connectors. Before crimping or soldering, make sure the individual stranded wires are nicely cleaned with some steel wool or other fine abrasive.