CVT / torque converter failure
The Ascent’s high-torque CVT suffers torque-converter shudder and outright failures; some vehicles got multiple transmissions under warranty. Watch for vibration around 30–40 mph under light throttle and revs that climb without the speed following. Subaru extended CVT coverage on many of these — verify by VIN, and walk away from any shudder that is not priced in.
Ask for repair records covering this item. If it hasn't been addressed and the car is in or near the mileage window, price the $2,500–$8,000 repair into your offer — or make it the seller's problem.