Hyundai Getz 2008: Ongoing problems since new

My partner bought a new Hyundai Getz 18 months ago and has had ongoing problems with it ever since. It had the front wheel bearings replaced before it had done 12,000 km, the passenger side power window failed, the central locking is over-sensitive, but the worst problem is that it suffers continual surging. The local dealership has fixed most of the problems under warranty, but cannot seem to solve the surging despite the car being returned to them on numerous occasions. Should my partner persevere with the dealer or is it worth seeking another mechanic to tackle the problem?