I agree. The sway is very likely correlated to the way the trailer is loaded. Also triple check the hitch setup. Height, and bar adjustment.
I have a XLT 302a Powerboost with a 157" wheelbase and my payload sticker is 1610 lbs.
Possible that this question has been asked before; is there a way to completely disable the Sync 4 navigation? I just want to use the Car Play Google Maps and Waze.