Under the clamshell (engine access) panel there are two convertible top cables on both sides of the car. They have a ball on the end that needs to be attached to the car. These have to be removed to get to the engine, so maybe the shop didn't replace these and there is not enough tension in the top.
This is a link for for a filter change but it shows you the ball cables (pic #2) and also the clip that attaches the rear of the top (pic #3) to the rear of the vehicle. In pic #3 the right hand side of the pic is the back of the car.
DIY: Air Filter
Threaded Mode
