Wagon “swimming” & chassis noise

Vehicle: S60, mileage 100,000KM, drive the car for 6 years in first possession without problems. For several weeks the following symptoms occur: – extremely side wind sensitive from 120KM/h, from 160KM/h dangerous. Car “floats” in the lane. – clean curve line from 160KM/h practically non-mobile, constant steering corrections necessary. Alternating curves from 160KM/h dangerous. – Cars now slings even minimally when changing lanes or braking in curves in urban traffic. – Dry “Klock” Geräu condition: – checkbook maintained at Volvo, first possession. – V&H damper at 70%, just tested on the test bench at DEKRA. – transverse handlebars and upper engine bearing new at approx. 65,000KM. – track rod head just renewed at inspection, suspension V&H remeasured. – steering gear probably in the case of inspection on stage at least no game during shaking on VR. – tyres now new summer tyres, Luf ddruck i.o., no improvement over winter tires. – otherwise no abnormalities / no further findings. Volvo workshop: “This can be anything possible”, “This can be expensive”. Does anyone have a little more idea of chassis and knows how to rationally limit the error without which the planless parts exchange??? I will definitely not get involved in that.