Below is a post I made in the towing forum yesterday in response to an OP that had severe sway problems with a moderate sized trailer on a decent truck. I thought air bags could be his problem.
Do you have air bags? I've seen the scenario more than once ( especially with on board compressors) where the driver loads the weight distribution with the bags under low pressure. They then air up the bags to level the truck and go higher than the unloaded height. This has the effect of unloading your weight distribution bars. If your hitch has anti-sway incorporated with weight distribution then the anti-sway effectiveness goes away. It also stiffens the rear suspension creating a fulcrum which unloads the front tires. The trailer is now nose high and starts to sway, the driver freaks and adds more air to the air bags making things worse.
Your weight distribution system should bring your hitch up to 1" below your unloaded height. Your air bags should be deployed to raise the truck to unloaded height only.
I was following my son and his trailer was dancing all over the place. I called him over to the side of the road where we unloaded the air bags and increased his WD springs by a link. Completely different tow. Many think air bags are a panacea, they aren't.