Here's a screencast of the bug in action, in a test case:
Unable to display content. Adobe Flash is required.
By the end, all sound clips are out of place.
(As you know, the F11 key is useful in viewing something as large as this screencast - to get to full screen in a browser if needed.)
When I get some time, I'll try to determine what triggers the anomaly. It is not a simple matter. Sometimes things work, sometimes they don't. It might be related to having a sound clip on a boundary between two video clips. But even if so, that isn't the sole factor.
Thanks for your reply, at least I now know that the procedure does sometimes work.