Lots of things can be a problem, but I recommend spending a couple hours with that WDH. Tilt the head angle more and fewer links under tension. Spend $15 at a CAT scale sounds like a cheap potential solution compared to many other ideas that are speculation and potentially costly to change.
3 passes with 3 axle weights
Truck alone
Truck with trailer without WD bars
Truck with trailer with WD bars
Truck front axle
Truck rear Axle
TT axles (both)
If your front axle weighs 3200 pounds alone, trailer tongue on ball may give up 300 pounds to 2900 pounds. Adjust that WDH to get back to 3200 pounds.