A few years ago TJ was checking me for bubbles at P3. He signaled "Up!" On the surface he said, "Your wing is leaking." Examination on shore showed that the base of the hose had separated from the bladder. I rented a wing from Cathy, and did the dive without further incident.
A few days ago Nicolas Casella was checking me for bubbles at Ponderosa Cenote. He signaled "Up!" On the surface he said, "Your wing is leaking." Examination on shore showed that the hose had become misaligned on its seat. Nico rented me a wing from Alexandra's shop in Puerto Aventuras, and we had a good dive.
The moral is that tank valve O rings are not the only weak points in the system. Wings, and especially their valves, need constant checking.