2015 NEWMAR MOUNTAIN AIRE Engine Problems

I PURCHASED THE UNIT WITH 25,000 MILES. THE DEF SYSTEM FAILED ENROUTE TO THE DEALER I PURCHASED IT FROM AND FAILED AGAIN AFTER APPROXIMATELY 3,000 MILES AFTER REPAIR. THE ENTIRE DEF HEADER WAS REPLACED. THIS IS AN EXTREMELY DANGEROUS SITUATION WHEN THE VEHICLE GOES IN TO DERATE. MY MOTORHOME IS 53,000 LBS AND 45'. ADD A TOW VEHICLE AND IT IS VERY DANGEROUS WHEN THIS HAPPENS. I WAS HEADING TO LAS VEGAS NV FROM QUARTZITE, AZ WHEN THIS HAPPEND ON A TWO LANE HIGHWAY. NO PLACE TO PULL OVER TO EVEN CHECK ANYTHING. THESE DEF SYSTEMS CONTINUE TO BE EXTREMELY PROBLEMATIC. THERE NEEDS TO BE INVESTIGATION IN TO HOW TO KEEP THESE SYSTEMS OPERATING PROPERLY.