US 69 hiway is a trucking route between I-44 in ne OK down to DFW. It has section of concrete surfaces that my wifes 1500 chevy pulling a 18' 10k car hauler empty or loaded just kills me. It bucks hard.
However I can run my 16k gvwr 36' 6800 lb empty triaxle GN stock trailer over the same roads with her truck and its super smooth. (no I don't use her truck with this trailer when loaded but I do have to pony the empty trailer sometimes between sale barns/pasture loading pins/etc.)
Freeway hop...as we call it since man started pulling trailers mainly on concrete hiways. When I hauled for a living sometimes I would route around concrete hiways for that reason.
There is no single "thing" that will fix all combinations and there are many "things" that causes it. Most folks find trial and error remedy solutions worked for them.