AES audio issue..not quite sure

I am not quite sure if what I am hearing is an issue w/ my hardware, or the actual soundtrack of KOF 2002 but...perhaps someone knows?

The AES is modded w/ composite and s-video out, and I am running the audio and video from these ports. (s video and composite audio) System also has Unibios 2.2 as well.

When playing KOF tonight I noticed that the volume got 2x as loud as usual for about a second here and there, and only on one stage. (mexico) While I cannot remember this ever happening, it sounds like its part of the actual soundtrack.

Hard to tell..but Im guessing someone else in here would have an answer. Is it the game, or is the audio having issues?

Other than that the hardware works perfect, so hard to tell.

And of course I checked the cables on both ends plus the headphone volume as well to rule all that out.

So the volume also increases for a second through the headphone port?
Are you using an AES copy of KOF2002 or MVS (through a converter)? I have an MVS as well as an AES, so I can check MVS carts on both systems.
I'm assuming it's stereo audio (ie two RCA jacks, red and white)?
Maybe you could try other games (on the same format AES or MVS) and see if they have the same problem.
Also it might be a problem with how the mod was done.