It could be either or both; but lag is usually meant to describe the delay between activation and the cruise beginning to take over; typically your speed falls off a few mph before climbing back up to set speed. Resume lag seems to be complained about less. Undershoot is usually meant to mean the bike, when accellerated above cruise and then left to coast back to cruise set speed, slows down to a speed less than the set speed and then regains. Overshoot; rarely complined about, is when one has used the resume feature to increase speed back up to cruise set and the bike actually exceeds the set speed before setteling back to cruise. Many GL1800 riders notice lag and undershoot. Many of those find an easy fix for the lag; most never figure out how to cure undershoot. Lots to search out; if you want to read more.