Package files contain banks, which contain sound data (including the raw PCM data).
If BankSize is too big, the game will read too far on the last sound, which often causes a segmentation fault. The BankSize field must be updated if the size of the bank changes, especially if the size increases, because the game works out the length of each sound the same way as the calculateBufferSize function displayed below.
Note that the game uses hardcoded indices to reference specific banks, so changes in order can lead to problems.