I guess we need to know what YOUR definition of 'chucking' is?
Chucking is something that can happen at start out or stopping or anytime there is fore and aft movement between the tow vehicle and trailer and is usually caused by slop in the hitch jaws to pin box or movement from a slider hitch.
Sometimes bucking or porpoising is often mistakenly referred to as chucking and is most times caused by highway expansion strips, uneven road pavement or an improper hitch set up.
Here is how eTrailer defines chucking...
"What is chucking?"
"Chucking and jarring while towing a 5th wheel trailer (or any trailer for that matter) is unavoidable because the trailer itself is not one piece with your vehicle. When your truck starts to move forward from a stop your trailer is still sitting static and so there will be a slight jolt; the same thing happens when you slow down. Since the front end of your trailer is connected to your truck, when your truck starts to slow down your trailer is still moving forward so it will give you a slight push at first."
Here's a video from LCI..