Update: Turns out m4a2s was extracting everything properly, it was the program I was using to convert .s files to .event files that was causing the error
Luckily it's super easy to fix and not an issue going forward.
Now I have everything except the GS synth instruments working properly, and I want to double check that my thought process is correct in how to handle them:
Some people have already extracted the instrument data, including the synths, into .sf2 format.
In this sample, each synth instrument has a bunch of different samples for each note(s), instead of the weird way they work in-engine. Theoretically, I should be able to extract these samples and make a multi-instrument out of them, then import them into a non-GS rom temporarily using Sappy, then re-extract the samples as .s files via Sappy, correct? This process looks like it'll be a ton of work so I just want to make sure I'm not completely off base from square 1.
Also, whenever I change an instrument in my middle stage rom (in this instance PMD Red Rescue Team, since I just had it lying around) to a multi instrument and press the 2nd edit button, Sappy mod 15 just instantly crashes
Any ideas on how to fix it?