With 45 days of "Market Time" patrols under her belt in 1968, "Warbler" returned to the coast of Vietnam in January 1969, and patrolled briefly near the port of Vung Tau. Later that autumn, "Warbler", in company with her sister-ship "Whippoorwill", departed Sasebo on 5 September, bound for Taiwan and Mine Exercise "Canned Heat." Unfortunately beset with mechanical difficulties, the ship went dead in the water in the Formosa Strait after attempted repairs at Keelung, Taiwan, had proved ineffective. Eight hours after the ship stopped,