I hope this information is useful to someone. 25 dives after a complete rebuild service for my Aqualung Legend LX I had my first stage fail shut at 60 feet 40 minutes into the dive. Fortunately my buddy recognized the international signal for out of air - eyes as wide as saucers - and he had his reg in my mouth ASAP. I had 1500 lbs left in the tank (although the gauge fell to zero until we got back to the boat). Took the regulator to a different Aqualung authorized service dive shop for analysis/repair and the issue was determined to be the ACD. From the dive shop - "We found that the ACD inner post valve and yoke nut had come loose." The regulator was rebuilt as listed on the intake documents and theses parts have been torqued to their proper specifications". So, holy cow - a bad service can result in a failed shut condition on the first stage with no prior indication that things are going south. Caveat Emptor.