What you are describing is how lockers work, they LOCK up and due to an extremely short wheelbase turning is not easy. They should be used only when you have an issue with traction, then turned off or you can damage your tractor. This is NORMAL behavior with lockers on any application.
I have a locker on my F 350 truck, F/R on my Jeep Rubicon and have used lockers almost 20 years, love them and would not own a mower of this type without them, in fact, it's mandatory where I live, which is why I am buying a TS348XD.
Let me know if you want to sell the tractor...