2018 BERKSHIRE BE43C-450 Engine Problems

Def Head Sensor problem or something related to Def. warnings come up say my vehicle is low on def when it is completely full. After 2 warnings I brought it in to a Freightliner repair center for an over $500.00 diagnosis and found it to be intermittent and have no answers but to proceed possibly until it could derate and go into limp mode (very slow crawl) while in the mountains on interstate highways causing unbelievable stress and safety issues. We've heard about this for years, why hasn't the gov't or EPA done anything to get the manufacturers to recall and remedy this? We should all be ashamed. We are an elderly retired couple who worked hard and save our money to travel our beautiful country and visit sickly siblings and have to deal with the idea we could be stranded for days, weeks or months. Do something now please!