I have the 8280WS, and have not had any such problems. I initially pulled with a Chevy 1500, and did have a fair amount of bounce, especially on I95 bridges. Still, we never had any breakage. I put on the Reese airborn, and it seemed to help a lot. I subsequently moved up to an F350 SRW, and the overall bucking improved even more. I still slow down a little for the bridge transitions in GA, and I seldom drive faster than 60. I'm not loaded to the max in the trailer, so I seem to have adequate travel on the torsion axles. If you have a dually, it is probably pretty stiff and the 8280WS pin doesn't provide much loading on the truck, so the Airborn or some other air ride would probably help.
2010 Rockwood 8280WS Fifth Wheel
2013 F350 Crew Cab SRW, Standard Bed PS Diesel
Reese Airborne Pin Box, Reese 16K Manual Slider
Camped 28 Days in 2012, 23 Days in 2013, 29 Days in 2014, 30 Days in 2015, 9 Days in 2016