Hi, we have a 12/18 EC that will not hold cruise control spend on undulating roads.If set to say 110 it will slow going down a gentle hill to say 94, stay there on the up hill for a few seconds then race to 118 well over the set speed setting.This is when the radar cruise is not picking up vehicles close by. The other problem is the emergency braking ,when set on cruise control it will activate the brakes by its self when you are merging from two lanes to one lane.It seams to pick up the vehicles coming from the opposite direction and jams on the brakes.Both these problems have been raised at the selling dealer who says that they are not a problem.No so good with a truck on your tale, location is Victoria Australia