I bought a 2018 Chevy 1500 Silverado High Country 4wd crew cab, in 1/24 96k miles, within 3 months it developed this issue your describing. I bought 3 GM products in the last half a dozen years, all 3 have issue 2 major issues! I retired in 2012 from a 30 year career as a professional Automotive Technician. I've always been a GM fan have a brother who worked for GM and retired. It's looking like this is my last GM!!!