2003 Ford Focus Front end

This car has over 225,000 miles on it. the trans has been replaced. Recently we have had front end problems. We had the tie rod end replaced, twice. New tires, twice. This time we have a new mechanic, who comes highly recommended. He told us that the tie rod end was not properly attached. He fixed that, and replaced the struts, which were original to the car. He replaced two ball joints. He took the car for a test drive, and noticed that when he turns the wheel to the left a little bit there will be a sudden jolt. He said it almost feels like someone is giving you a little push from behind. He went back in and checked all his work and he finds nothing that would cause this.