OP
So from the letter they are claiming that all is well and they have fixed all issues. Of course test it when you get it back and see if it really is completely fixed. Frankly, I'd probably go trade it in on some other new one myself.
Back to some of the technical issues: The whole topic of reducing loading on the front axle is pure nonsense. Your 4-in-1 bucket weighs 400kgs. That is only 880 lbs. My 2660 tractor is very much the same size and capacity as yours, just older model. My 4-in-1 bucket weighs a little over 1000 lbs -- 120 lbs more than yours -- and has never been a problem plus I often pick up a full load of mud in it while cleaning out springs (!!) OK, I do keep a 1400lb bush hog on the back all the time so I do have plenty of ballast. Mr.Hill stated that the 400kgs bucket was "too heavy for the tractor." That is bull. Not so. Silly. There is no way on this earth that a 400kgs bucket on that tractor made the rear wheels "light" even with no ballast of any kind ! That is the opposite of truth with my fake apologies to Jake Kerr. The counterweight on the rear will have a very small effect on the load on the front axle -- any junior engineering student can see the lever lengths rule out rear 3pt loading having much effect on front axle loading. Being "required" to use a rear counter weight is absurd in spite of the fact that they claim it and you agreed to the terms. The claim that lack of a counter weight on the rear "accentuated" the aggressive shuttle change is completely bull. The power shuttle either engages and disengages properly or it does not. ****, take the bucket OFF if they are claiming that causes wild lurching when using the shuttle !! It won't take long to prove that is nonsense.
Anyway, if this thing works OK when you get it back I would trade it in as soon as I could and get as far away from it as I could. For one thing, you know you don't have a competent dealer service shop -- they proved that. So what ever happens next you cannot trust them to fix it. Find a good, competent dealer and buy some other tractor from him.