On our Fifth Wheel I checked the wiring several times. I found wires to right side damaged and no braking going on once and just like things to be perfect, I made sure all the connections were not corroded, tight and covered with dielectric compound and a sleeve. I thought about replacing the wires as I thought they were marginal in size but didn't.
Had one wheel with magnet bad. I adjusted them before every long trip, a pain but I was skinnier and younger. Changing them to stainless rotors with no lube bearing assemblies would solve all that, but like me, by the time I got it done I would trade it.