AIR 2.7.1 breaks sound clip in existing app

AIR build 19610 has produced strange behavior in an existing app that has been published and installed since AIR 1.5.

There is a clip onstage (using Flash CS5) which contains sound on its timeline, as well as some simple timeline code (AS3). Certain behavior in the app moves the root playhead to different timeline locations. The sound clip never goes out of scope. At a certain point, for some still-unknown reason, a "ghost duplicate" of the sound clip starts to loop, playing its sound, but without any of the timeline code. It's a "ghost duplicate" because the original sound clip onstage continues to function normally; it doesn't play, and its timeline code is still functional. In testing, I can create other clips onstage that contain sound, with a simple stop() command, and they fail the same way. Different timeline movements can make more ghost duplicates, creating overlapping sounds.

It seems specific to build 19610, since repeated tries with the previous build, 19530, showed no problem. The problem immediately showed once I updated to 2.7.1 in any environment; XP, Win7 or Mac.

I'm trying to work out a simple general case, but the problem only shows when building the complete (and very complex) SWF from the original FLA. Any insight? Thanks.