Advancements/ Achievements Reset

I started this hardcore world on a separate client called Essentials with Optifine and other things like Fullbright, and have since moved the world files over to the vanilla Minecraft launcher. But sometimes when I join my world I'll receive "Sky's the Limit" and I'll check if my advancements reset and sure enough they did. This has happened twice now and I'm looking for a fix? Maybe to delete the mod pack in the world files? please help!