Disney Speedstorm (Gameloft Jet Engine) - small file that gets larger after every patch

[SgtSweetieBelle]

over in audio we've been working on extracting the sound files from Disney Speedstorm, which runs on developer Gameloft's proprietary Jet Engine.

the pack_sd.pack archive contains all audio files (BNK/WEM, WAV), with 16-char alphanumeric filenames and no metadata.

i've extracted the audio files from every version of the game since launch.

i noticed that every game version's pack_sd.pack archive has a single file in common — 397F9F6720B1625D — that seems to grow larger with each and every patch:

...which makes me strongly suspect that it's some kind of index or manifest containing metadata for all of the other BNK/WEM and WAV files in the pack_sd.pack.

because of that, i'd like to see if there's a way to identify and read this file, in case it might help with identification and labeling.

here's what i've done so far.

• ran it through signsrch to no avail.
• ran it through comtype_scan2 but i'm still combing through the results..
• popped them into a hex editor, and there's no obvious compression that i can recognize.
• when i compare the Season 4 and Season 9 versions of the file, i notice they share many chunks in common at fixed intervals:
  

that's everything i've thrown at it so far. does any of this strike a chord with anyone?

if anyone wants to take a crack at it, here's a ZIP containing every version of this file from season 4 to season 9:

• 397F9F6720B1625D.zip

any help would be much appreciated!