Chucking?

Best method to minimize "chucking" is to make sure your trailer is frame level when towing, weight is properly distributed, and the trailer suspension is fully functional with some type of energy dampening system (shocks, air bags, cushioned equalizers).

Many, many trailers have no suspension energy dampening systems(cheap OEM builders)-these trailers will have a propensity to chuck and have other poor handling traits because a harmonic cycle gets started and doesn't stop. These harmonic cycles are what you are feeling as chucking.