I had the same thing happen a couple years ago on my BX2200, which is now about 16 years old and about 1300 hours.
Anyway, I finally got it out of the rear PTO position. Took a bit of trying. Gentle force on the handle but not much. I may have tried repeatedly engaging the pto and disengaging it until I got it to move.
DO NOT FORCE IT! is my advice. Take your time, try many times, and you will succeed.
I now tied my selector lever in the mid pto position with a piece of wire. The experience was that traumatic.
I do not need the rear pto on the BX. I know it is best to change things now and then but I do not need that worry/hassle again. It can stick in the mid pto position for all I care. But I have the larger tractor which I use the rear pto on, but not the mid. So that one can stick in the rear pto position for all I care.
Now for a bit of fatherly advice. When you start to get frustrated, stop and start again another time. No need to force and break something that does not need broken.
Edit: I think that is what RCW said in one sentence...