2015.5 Volvo S60 Steering Issue

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The steering on my 2015.5 S60 T6 Platinum with 19 in. wheel and sport suspension is not precise (loose) and overly light (too much power steering assistance) ONLY during 60+ mph on twisty freeways.

I believe the problem is in the EPS (Electronic Power Steering) system. According to Polestar, my car has the new fully electronic steering, whereas in the past it is only partial. Monitor by sensor(s), the EPS system has variable assist, which allows for more assistance as the speed of the Volvo decreases and less assistance from the EPS system during high speed situations. The nature of EPS versus traditional hydraulic power steering is that it is easily adjustable/tunable. According to Clemson University Vehicular Electronics Laboratory, one can alter the steering weight to radically improve steering feel and high speed stability. Furthermore, the ECU (Electronic Control Unit) evaluates:
1) the steering torque, 2) the steering direction being applied by the driver, 3) the road speed, 4) electric motor to provide the required amount of assistance in the correct direction. A poorly functional ECU can cause poor steering response. In certain instances, a simple reprogramming of software or replacement of torque sensor(s) is needed to increase precision safe steering.

After recently driving a loaner car, a 2015.5 S60 T5 Premier with also 19 in. wheel and sport suspension, on the same twisty freeway, the loaner has more accurate steering than my T6 Platinum no matter what steering mode my car was set. The chassis difference between my car from the loaner is an additional supercharger and my EPS system has the feature to adjust between light, medium, or heavy, whereas the loaner is fixed.

What are the possible problems with my electric power steering system that can cause this poor steering issue?