One part of the FCS in the 2S38 has no function, according to the in-game x-ray viewer.
Only the part in the crew compartment has any functions and thusly it is only this part that will actually have an impact when destroyed.
As you can see, the unit mounted in the turret has no function what so ever and thusly does not impact the vehicle when destroyed/Damaged negation the whole function of the FCS implementation for this vehicle.