I read somewhere of jumpy throttle control complaints on the 850. In the 90s I had a gator with a jumpy, over sensitive throttle. JD came out with what they called a "rough terrain kit" that helped the issue. It was basically a damper assembly that mounted to the gas pedal and worked well. It was not a recall...you had to complain and ask for it and they would install free..at least my dealer did. Maybe kubota has something similar available.