After some extended time extracting your mod, I finally able to find the end scenes. You really ought to optimize your mod by removing unused files, Diversee
Back to topic, after some tests, I discovered that the issue is not the oggs but the gifs. Your end gifs are not animated therefore they are played very quick and thus there's not enough time to play any music. I believe other gifs in scenes folder aren't animated also.
So to solve your problem, you need to set delay to your scene gifs to give time for player to watch them and music to be played

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