I read through the forum and cannot find my exact issue, so I apologize if this question has come up elsewear. I recently got a 17' TT Forest River 17bhse, towing with a 2015 f150 with a class 3 hit...
Inflate tires to 5 psi less than max in the cool of morning before it is driven. Also add approx 150 to 200 lbs to tongue weight. Set trailer at level or slightly nose down. It may not be just one thing but in most cases the above will cure the problem. Last thing if above does not cure then change to a TV tire with stiffer walls.