Potentiometer knight trailed sprayer

[mcdonap2]

Asked a question here before re a knight sprayer and got a lot of helpful answers so hopefully somebody can shed a light. Basically Ive a knight trailed sprayer. The potentiometer works fine insofar as when the tractor turns, the potentiometer turns and the hydraulic ram extends/retracts to operate the steering on the sprayer. The only issue is it doesn't steer enough and ends up understeering. It's a smartrac system so obviously I went To the control box and steering calibration part and pressed the plus to increase the steering but the maximum turning is still understeering ie when I'm turning the tractor as sharp as possible the sprayer steering ram is only 75% retracted when it should be 100% retracted. The interesting thing is that if I press the minus button on the steering calibration I can get way more understeering than I could possibly need. I was rooting with the wires before so it's possible that something could have been put back wrong but I pretty sure everything is the way it should be. Any help appreciated

 

[Lincsman]

Mine has a box with a giroscope in it (I think??), it sits on the tractor and works out the difference, and corrects according to speed etc maybe yours could be upgraded?