To me it sounds like front end bottoming out and hitting something. Maybe coil spring is getting all the way compressed.
Going freeway speeds and coming off a bridge deck back onto regular road sometimes a bump at the same time TT is putting weight on front also.
Have you weighed your rig?
I should do that again. I lost my old scale numbers from about a year ago and haven't added any weight. But do remember my tongue weight came in at 12%. What did surprise me is the difference in front axle empty compared TT hooked up was only 100 pounds more placed on front axle.
It's a 2 wheel drive. TT is a 2013 Arctic Fox 25W.
Weight of TT is 6800 according to OEM. But many owners say OEM numbers are not good and weights are actually more. And that is before adding anything you need to bring along.
I also remember all my numbers were well within spec's.
Think I'll start with new shocks and go from their.