Once bought a Fendt 312 ex demo. It was a dog the whole time we owned it and most of the issues was down to the brakes disintegrating into the back end. So brake issues, hydraulic issues and then eventually vario out, turbo went etc . Got rid of in the end swapping for a brand new 412 which was very reliable. Swore I would never touch a demo again the hassle it was for only a small saving.