Ts18Q7

Hey there. I have an 18 Q7 prestige, 90k miles. Just put new vredestein tires 15 months ago. 12k miles ago. Rear driver side has been 2 inches lower for at least 2 years. Upon state inspection, mech says found a broken rear spring. He replaced both rear springs and shocks. Since then the ride is nowhere near the same. Dry road it feels loose on uneven road or potholes. Now it's winter and the truck feels super loose like its sliding on snowy or icy roads even at 30 mph. I took it back to mechanic and he says must be the tires... Should I take it for an alignment somewhere else? Not sure what to do. Hubby thinks I'm nuts...