I just replaced my side marker lights... If mine are any indication, Newmar doesn't do a good job of sealing the lights from moisture. The wire on mine had just corroded off the light fixture. Mine were also located in the rear wheel well, so when driving in the rain...
Anyway, I ended up ordering new lights from Command. They also had a gasket that Newmar didn't use. It looked like they used a liquid gasket material. I used some silicone to seal the opening from the gasket to the light. Hopefully that will stop the water penetration.
Millard & Sherry
2019 Mountain Aire 4018
Toad 2014 Honda CRV or 2019 GMC Canyon
M&G Braking-Roadmaster Towbar