With Adaptive Cruise Control on, without touching brake or cruise controls, while passing semi trucks (also happens but less frequently with all vehicles), the Adaptive Cruise Control will pause or disengage, causing the vehicle to lose speed and momentum. Vehicles trailing the vehicle at this time are not aware of this sudden change in constant speed, creating a potential serious accident at highway speeds. Problem has occurred numerous time over the life of the vehicle (2 months). Is repeatable.