A couple of observations. I have a Scamp
19Deluxe and pull it with a 2013 Tacoma, so it is quite similar. When I towed it home the very first time (first 500 miles towing anything in my life), I was very nervous about what I would also describe as chucking. I did all kinds of research on hitches and found many different solutions. However, the problem went away after I increased the pressure to the Scamp
suggested 45 psi, instead of 32 to 35 which I towed with then, being uneducated and thinking in terms of car tire pressure. So try to pump up the tires
to the allowed maximum for your next trip.
All those "soft" hitches seemed to be complicated and expensive, so they were not going to be my first attempt at solving the problem anyway. There is a hint of it, but no big deal.
This kind of rig does have that tendency, it might be less noticeable with a heavier truck. Also, there are some highways and interstates that have a wave built in that makes this quite unpleasant. They are usually those concrete new ones. I wonder what is wrong with those concrete finishing machines.