You have adjusted the pushrods on the brake master cylinders, BIG mistake!!!. Reset them back to give 1mm of free play on the pushrod, otherwise brakes will come on when the tractor warms up. To adjust the brakes on a 6211 with disc brakes you need to remove the plastic covers on the rear of the transmission, jack up the wheel handbrake off tighten adjuster untill wheel will just turn, then slacken adjuster nut 1/2 turn, repeat on other side, then try brakes if unbalanced slacken adjuster on the brake that pulls hardest untill you reach the brake balance!