On a previous unit, the low-quality factory original speakers did much the same after two seasons. I replaced them with a pair of good quality marine-grade speakers that I ordered on-line. Much better sound, never a problem, as they were designed to get wet!
Be Safe, and Everyone Goes a Home,
2014 RAM Laramie 2500 w/6.7L Cummins Diesel and Automated Safety Hitch
2016 377RLBH Jayco North Point
300W of Suntech Solar w/Rogue MPPT Controller & Xantrex 2000W PSW Inverter