2013 Pete 389 Air Trac problem

2013 Peterbilt 389 glider 18 speed. We haul heavy everyday for the most part right around 100k or more. Started doing this weird thing where it will dive out on the right rear and pick the left side of the truck up along with tipping the trailer to the right, donations at a dangerous angle. My boss and our mechanic do not believe that it is happening this bad. But they have not driven the truck. Sometimes it will come out of it and act fine other times it acts like this all day Wondering what may cause this? Have checked over completely and nothing seems broken. Possibly an airbag issue? Or leveling valve? Anybody ever experienced this before? Any help would be greatly appreciated!