If you has custom sound for challenge complete, and you also rename the advancement in lang file (at least 2, any, title or description). Then the custom sound didn't get play
How to reproduce
1. Make recourcepack
2. Make lang file
3. Put this in en_us.json

{ "advancements.nether.fast_travel.title": "Subspace Bubble", "advancements.adventure.bullseye.title": "Bullseye" }

4. Put this in sounds.json at assets/minecraft/
{
"ui.toast.challenge_complete":

{ "sounds": ["minecraft:challenge_complete"] }

}
5. Put challenge_complete.ogg in assets/minecraft/sounds
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Then if you playsound the challenge complete, it play the default one. but if you remove one of them, it play the custom one.
Is this a bug?