You need to look under the rubbers on the steering rod/gearbox and check for rust.
Loosen the covers on the side of the gearbox, turn the wheels so that you can see as much as possible, and even if it is ok, lubricate it prophylactically.Such a defect is immediately revealed by lifting the car with two wheels.The steering wheel should then go practically by itself, and if you need to use any force, you can be sure of it.Other faults relating to the gearbox with the electric steering causing the lack of straightening of the wheels, and not giving other symptoms, are rather beyond the scope of your repair capabilities and it is better that you do not dig around there.
Another element is the pins, they can also cause such a situation, but with this type of suspension it is extremely rare, applies to cars that are not driven much, and in addition, the problem quickly disappears in favor of play and it happens quickly.The fact that the steering wheel does not return, is certainly not caused by a defect in the power steering and I would not even look there.
The power steering only works when a greater torque is required on the steering wheel, until then there is nothing there to help because there is no need for it.
The power steering is a tracking system, you need to turn the steering wheel a fraction of a degree to activate the actuator or motor in the case of an electric system.The wheels should return by themselves without touching the steering wheel, just as in a car without power steering.Connecting to any computers in this case does not make any sense.
I don't bet on it,but it wouldn't hurt to check the rubbers well,because it is their leakage that gives such a result.
From experience I know that 99% of damage to all components equipped with a ball joint begins with a broken cover.
It would be good to get to grips with the subject, because any fault that causes resistance, ends only in two ways, namely rapid wear and play or blockage.
The cause may also be the suspension geometry and contrary to popular opinion does not necessarily then eat the tyres .
What about the column bearings themselves, I advise you to check on the ground and do not lift the car.