I'm not really sure that they did actually change out the sound system. The main reason why the audio is out of sync for the corridor scene, is that the "audio skipper" as I call it doesn't work anymore. What this did back then is that when the doors on the corridor scene started to open, it would skip ahead to the vibraphone part of the audio(after the drums), which made it synchronized. There were some videos of recent times to where once in every few weeks, it decides to start working only a few times, but it did it at a random time in the audio, such as when the stars would come on, I heard it skip ahead in the audio. In late 2009, Disney decided to "fix" the problem of the quiet bit that happened most of the time after the glass broke(due to the timing of each AGV after Tower4) by making Bravo and Charlie play the longer starting audio that Alpha and Delta use, which made it WAY off sync but it meant there was no gap between it and the transition to the 5th dimension scene audio. Disney also made Delta's and Alpha's starting audio delayed a few seconds, to make it match with Bravo and Charlie. This change was reverted sometime in 2013 but I believe they never re-enabled the audio skipper when it was disabled for the change in 2009. There was a time in 2014 where they made Delta(possibly Alpha as well) play the shorter starting audio Charlie and Bravo use, and this made it perfectly synchronized. They also did a sort of better approach of the quiet bit by just making it play the transition audio even if the computer thinks its not ready to head up yet.
The drop profile audio problem is different. When the drop profile initiates, the audio for it plays, but the actual drop sequence for the VVC doesn't begin until seconds after. It is worse on Foxtrot(about 3-5 seconds) than Echo (about 2-3 seconds).
