2016 FOREST RIVER SOLERA Electrical System Problems

Two Incidents: 1) June 4th: Going down a ~8% grade at approximately 25-30 MPH, towing an aluminum boat with working electric trailer brakes (~3000 lbs on trailer). The road was paved, dry and in good condition, no gravel. I was coasting in 2nd gear (manually selected) and vehicle was maintaining speed with no additional brake applications. I was not accelerating or decelerating. On it's own, the vehicle then downshifted into 1st gear taking the engine above redline, at the same time, the rear axle began hopping (actually skidding / chirping tires quickly), the engine began stalling / starting (Bucking), then the vehicle applied the throttle (again - no input from me) accelerating downhill. I pressed the brake pedal, but the pedal went to the floor and you could feel the ABS system was active, trying to prevent a ficticious skid. I shifted the transmission to neutral, and manually applied the...