[CS6] [AS3] Understanding odd animation disparities relating to sound settings?

Hello. This is related to something that I am currently experiencing whilst working in Flash Pro CS6 and using Actionscript 3.

I'm relatively new to the software in terms of experience, and was wondering about some odd behavior I've been seeing, wherein qualities in the animation differ with respect to my sound settings. This isn't a problem that needs fixing, per-se, as it's mostly just down to timing issues, but I would like to understand this behavior so that I know what to expect in the future.

I have a fairly complex flash animation with multiple scenes, some actionscript-controlled objects and musical accompaniment. This music runs throughout the entire animation, and the animation is synchronized loosely with the music. Oddly, I have recently noticed that, depending on the settings which I choose to apply to this music track, the visual component of the animation behaves differently. I should add that, in the flash editor, my music and animation are synchronized perfectly.

If I set the music to "Stream", and render as a flash file, then several sections of the animation lag horribly. The synchronization between music and animation remains exact, but I see horrible jerky movement on screen. If I set the music as an "Event" sound and then render, however, not only is the music (understandably) much better quality but this lag disappears. However, for some reason, on one particular scene of the animation, where the lag during "streaming" is most severe, the sequence of timeline events appears to slow down with respect to the music. You must understand that this scene is contained within it's own movie clip, placed directly onto the timeline with only a few fade transition objects on the layers over it. The content within this movie clip plays entirely lag free and at the correct speed, as does the rest of the flash, but the scene/movie clip remains on the screen for far longer than previously with respect to the music, despite it being synchronized perfectly on the timeline. The fade transition events on the layers above the movie clip also occur later than they are scheduled, as if the "scrolling line" on the timeline were moving more slowly over the movie clip, despite the apparent lack of lag.

Of course, I can solve these problems by setting the sound as an event sound whenever I export to a flash file, and reducing the length of the scene manually until it lines up with the music in the render. However, I would like to better understand how my sound settings are affecting animation lag and timings. Presumably setting the sound as an "event" pre-loads it before the flash - is this also causing the rest of the flash to pre-load, hence removing the lag? Will this increase the time that my exported animation takes to load in it's preloader screen? Why are the timings affected by setting the sound to "Event", especially seeing as there is no visual lag or jerkiness and it only occurs when playing this one movie clip?

Any answers to these questions would be most welcome.

Thank you for any responses.